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	$189.25	6.833%	$202.1815	$202.18	$202.20	$202.20
Purchase #2	$120.64	5.799%	$127.6359	$127.64	$127.65	$127.60
Purchase #3	$5.42	6.397%	$5.7667	$5.77	$5.75	$5.80
Purchase #4	$111.50	10.677%	$123.4049	$123.40	$123.40	$123.40
Purchase #5	$26.38	6.685%	$28.1435	$28.14	$28.15	$28.10
Purchase #6	$215.94	3.317%	$223.1027	$223.10	$223.10	$223.10
Purchase #7	$64.33	10.525%	$71.1007	$71.10	$71.10	$71.10
7 purchase totals =	$733.46		$781.3359	$781.33	$781.35	$781.30