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	$184.94	5.753%	$195.5796	$195.58	$195.60	$195.60
Purchase #2	$107.46	3.446%	$111.1631	$111.16	$111.15	$111.20
Purchase #3	$113.91	11.670%	$127.2033	$127.20	$127.20	$127.20
Purchase #4	$191.74	10.563%	$211.9935	$211.99	$212.00	$212.00
Purchase #5	$174.95	5.758%	$185.0236	$185.02	$185.00	$185.00
Purchase #6	$82.58	6.801%	$88.1963	$88.20	$88.20	$88.20
Purchase #7	$90.87	9.140%	$99.1755	$99.18	$99.20	$99.20
7 purchase totals =	$946.45		$1,018.3349	$1,018.33	$1,018.35	$1,018.40