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	$132.52	5.690%	$140.0604	$140.06	$140.05	$140.10
Purchase #2	$88.86	12.299%	$99.7889	$99.79	$99.80	$99.80
Purchase #3	$50.58	13.784%	$57.5519	$57.55	$57.55	$57.60
Purchase #4	$211.43	5.280%	$222.5935	$222.59	$222.60	$222.60
Purchase #5	$127.96	11.362%	$142.4988	$142.50	$142.50	$142.50
Purchase #6	$114.84	3.146%	$118.4529	$118.45	$118.45	$118.50
Purchase #7	$224.77	11.794%	$251.2794	$251.28	$251.30	$251.30
7 purchase totals =	$950.96		$1,032.2258	$1,032.22	$1,032.25	$1,032.40