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	$135.56	13.401%	$153.7264	$153.73	$153.75	$153.70
Purchase #2	$167.69	10.227%	$184.8397	$184.84	$184.85	$184.80
Purchase #3	$145.85	11.604%	$162.7744	$162.77	$162.75	$162.80
Purchase #4	$212.76	4.647%	$222.647	$222.65	$222.65	$222.60
Purchase #5	$235.92	12.167%	$264.6244	$264.62	$264.60	$264.60
Purchase #6	$48.46	3.250%	$50.035	$50.04	$50.05	$50.00
Purchase #7	$139.66	7.336%	$149.9055	$149.91	$149.90	$149.90
7 purchase totals =	$1,085.90		$1,188.5524	$1,188.56	$1,188.55	$1,188.40