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	$224.67	10.240%	$247.6762	$247.68	$247.70	$247.70
Purchase #2	$114.60	10.455%	$126.5814	$126.58	$126.60	$126.60
Purchase #3	$62.92	6.556%	$67.045	$67.05	$67.05	$67.00
Purchase #4	$142.56	7.309%	$152.9797	$152.98	$153.00	$153.00
Purchase #5	$54.69	3.336%	$56.5145	$56.51	$56.50	$56.50
Purchase #6	$245.27	3.354%	$253.4964	$253.50	$253.50	$253.50
Purchase #7	$35.89	13.725%	$40.8159	$40.82	$40.80	$40.80
7 purchase totals =	$880.60		$945.1091	$945.12	$945.15	$945.10