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	$199.32	10.257%	$219.7643	$219.76	$219.75	$219.80
Purchase #2	$89.80	10.695%	$99.4041	$99.40	$99.40	$99.40
Purchase #3	$14.92	10.422%	$16.475	$16.48	$16.50	$16.50
Purchase #4	$204.69	8.701%	$222.5001	$222.50	$222.50	$222.50
Purchase #5	$99.84	7.664%	$107.4917	$107.49	$107.50	$107.50
Purchase #6	$227.58	9.205%	$248.5287	$248.53	$248.55	$248.50
Purchase #7	$36.35	3.802%	$37.732	$37.73	$37.75	$37.70
7 purchase totals =	$872.50		$951.8959	$951.89	$951.95	$951.90