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	$192.47	7.201%	$206.3298	$206.33	$206.35	$206.30
Purchase #2	$153.60	10.523%	$169.7633	$169.76	$169.75	$169.80
Purchase #3	$120.32	10.817%	$133.335	$133.34	$133.35	$133.30
Purchase #4	$142.81	11.310%	$158.9618	$158.96	$158.95	$159.00
Purchase #5	$106.59	5.586%	$112.5441	$112.54	$112.55	$112.50
Purchase #6	$201.32	10.323%	$222.1023	$222.10	$222.10	$222.10
Purchase #7	$181.91	3.619%	$188.4933	$188.49	$188.50	$188.50
7 purchase totals =	$1,099.02		$1,191.5296	$1,191.52	$1,191.55	$1,191.50