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	$142.30	7.745%	$153.3211	$153.32	$153.30	$153.30
Purchase #2	$148.74	11.797%	$166.2869	$166.29	$166.30	$166.30
Purchase #3	$123.41	3.327%	$127.5159	$127.52	$127.50	$127.50
Purchase #4	$161.32	6.552%	$171.8897	$171.89	$171.90	$171.90
Purchase #5	$90.47	4.568%	$94.6027	$94.60	$94.60	$94.60
Purchase #6	$236.52	3.299%	$244.3228	$244.32	$244.30	$244.30
Purchase #7	$221.59	11.485%	$247.0396	$247.04	$247.05	$247.00
7 purchase totals =	$1,124.35		$1,204.9787	$1,204.98	$1,204.95	$1,204.90