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	$120.91	5.320%	$127.3424	$127.34	$127.35	$127.30
Purchase #2	$199.75	8.356%	$216.4411	$216.44	$216.45	$216.40
Purchase #3	$77.44	6.384%	$82.3838	$82.38	$82.40	$82.40
Purchase #4	$125.67	4.829%	$131.7386	$131.74	$131.75	$131.70
Purchase #5	$144.98	12.673%	$163.3533	$163.35	$163.35	$163.40
Purchase #6	$89.98	10.463%	$99.3946	$99.39	$99.40	$99.40
Purchase #7	$199.95	6.195%	$212.3369	$212.34	$212.35	$212.30
7 purchase totals =	$958.68		$1,032.9907	$1,032.98	$1,033.05	$1,032.90