Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$173.38	11.505%	$193.3274	$193.33	$193.35	$193.30
Purchase #2	$140.57	5.860%	$148.8074	$148.81	$148.80	$148.80
Purchase #3	$227.34	6.808%	$242.8173	$242.82	$242.80	$242.80
Purchase #4	$96.84	8.484%	$105.0559	$105.06	$105.05	$105.10
Purchase #5	$141.88	13.180%	$160.5798	$160.58	$160.60	$160.60
Purchase #6	$162.83	11.233%	$181.1207	$181.12	$181.10	$181.10
Purchase #7	$114.76	4.424%	$119.837	$119.84	$119.85	$119.80
7 purchase totals =	$1,057.60		$1,151.5455	$1,151.56	$1,151.55	$1,151.50