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	$96.56	8.718%	$104.9781	$104.98	$105.00	$105.00
Purchase #2	$219.58	10.826%	$243.3517	$243.35	$243.35	$243.40
Purchase #3	$39.62	6.790%	$42.3102	$42.31	$42.30	$42.30
Purchase #4	$64.76	4.284%	$67.5343	$67.53	$67.55	$67.50
Purchase #5	$191.40	9.438%	$209.4643	$209.46	$209.45	$209.50
Purchase #6	$216.71	11.750%	$242.1734	$242.17	$242.15	$242.20
Purchase #7	$150.77	13.459%	$171.0621	$171.06	$171.05	$171.10
7 purchase totals =	$979.40		$1,080.8741	$1,080.86	$1,080.85	$1,081.00