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	$171.87	11.474%	$191.5904	$191.59	$191.60	$191.60
Purchase #2	$84.72	5.123%	$89.0602	$89.06	$89.05	$89.10
Purchase #3	$69.44	3.130%	$71.6135	$71.61	$71.60	$71.60
Purchase #4	$141.64	4.589%	$148.1399	$148.14	$148.15	$148.10
Purchase #5	$87.87	6.133%	$93.2591	$93.26	$93.25	$93.30
Purchase #6	$28.54	6.274%	$30.3306	$30.33	$30.35	$30.30
Purchase #7	$196.66	13.513%	$223.2347	$223.23	$223.25	$223.20
7 purchase totals =	$780.74		$847.2284	$847.22	$847.25	$847.20