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	$55.73	9.671%	$61.1196	$61.12	$61.10	$61.10
Purchase #2	$210.68	5.851%	$223.0069	$223.01	$223.00	$223.00
Purchase #3	$233.69	8.658%	$253.9229	$253.92	$253.90	$253.90
Purchase #4	$104.72	6.324%	$111.3425	$111.34	$111.35	$111.30
Purchase #5	$33.31	5.174%	$35.0335	$35.03	$35.05	$35.00
Purchase #6	$118.84	7.249%	$127.4547	$127.45	$127.45	$127.50
Purchase #7	$58.29	7.426%	$62.6186	$62.62	$62.60	$62.60
7 purchase totals =	$815.26		$874.4987	$874.49	$874.45	$874.40