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	$88.82	10.148%	$97.8335	$97.83	$97.85	$97.80
Purchase #2	$204.85	11.869%	$229.1636	$229.16	$229.15	$229.20
Purchase #3	$65.87	9.390%	$72.0552	$72.06	$72.05	$72.10
Purchase #4	$55.72	11.159%	$61.9378	$61.94	$61.95	$61.90
Purchase #5	$210.68	12.285%	$236.562	$236.56	$236.55	$236.60
Purchase #6	$159.67	5.161%	$167.9106	$167.91	$167.90	$167.90
Purchase #7	$221.57	7.362%	$237.882	$237.88	$237.90	$237.90
7 purchase totals =	$1,007.18		$1,103.3447	$1,103.34	$1,103.35	$1,103.40