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	$10.69	11.551%	$11.9248	$11.92	$11.90	$11.90
Purchase #2	$184.91	13.826%	$210.4757	$210.48	$210.50	$210.50
Purchase #3	$218.46	10.745%	$241.9335	$241.93	$241.95	$241.90
Purchase #4	$229.49	11.781%	$256.5262	$256.53	$256.55	$256.50
Purchase #5	$69.90	10.358%	$77.1402	$77.14	$77.15	$77.10
Purchase #6	$221.59	13.608%	$251.744	$251.74	$251.75	$251.70
Purchase #7	$90.94	5.584%	$96.0181	$96.02	$96.00	$96.00
7 purchase totals =	$1,025.98		$1,145.7625	$1,145.76	$1,145.80	$1,145.60