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	$154.51	11.339%	$172.0299	$172.03	$172.05	$172.00
Purchase #2	$112.27	5.135%	$118.0351	$118.04	$118.05	$118.00
Purchase #3	$62.95	13.327%	$71.3393	$71.34	$71.35	$71.30
Purchase #4	$198.50	4.819%	$208.0657	$208.07	$208.05	$208.10
Purchase #5	$73.68	12.728%	$83.058	$83.06	$83.05	$83.10
Purchase #6	$58.84	4.604%	$61.549	$61.55	$61.55	$61.50
Purchase #7	$134.67	12.180%	$151.0728	$151.07	$151.05	$151.10
7 purchase totals =	$795.42		$865.1498	$865.16	$865.15	$865.10