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	$67.34	5.242%	$70.87	$70.87	$70.85	$70.90
Purchase #2	$61.85	3.332%	$63.9108	$63.91	$63.90	$63.90
Purchase #3	$151.71	9.227%	$165.7083	$165.71	$165.70	$165.70
Purchase #4	$158.31	10.496%	$174.9262	$174.93	$174.95	$174.90
Purchase #5	$133.61	11.812%	$149.392	$149.39	$149.40	$149.40
Purchase #6	$173.41	7.180%	$185.8608	$185.86	$185.85	$185.90
Purchase #7	$229.25	6.216%	$243.5002	$243.50	$243.50	$243.50
7 purchase totals =	$975.48		$1,054.1683	$1,054.17	$1,054.15	$1,054.20