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	$33.47	4.719%	$35.0494	$35.05	$35.05	$35.00
Purchase #2	$58.51	6.468%	$62.2944	$62.29	$62.30	$62.30
Purchase #3	$148.69	9.171%	$162.3264	$162.33	$162.35	$162.30
Purchase #4	$26.97	3.147%	$27.8187	$27.82	$27.80	$27.80
Purchase #5	$152.62	6.109%	$161.9436	$161.94	$161.95	$161.90
Purchase #6	$211.72	4.672%	$221.6116	$221.61	$221.60	$221.60
Purchase #7	$114.84	7.344%	$123.2738	$123.27	$123.25	$123.30
7 purchase totals =	$746.82		$794.3179	$794.31	$794.30	$794.20