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	$166.75	10.141%	$183.6601	$183.66	$183.65	$183.70
Purchase #2	$87.75	5.369%	$92.4613	$92.46	$92.45	$92.50
Purchase #3	$186.87	5.164%	$196.52	$196.52	$196.50	$196.50
Purchase #4	$194.74	10.184%	$214.5723	$214.57	$214.55	$214.60
Purchase #5	$96.35	3.355%	$99.5825	$99.58	$99.60	$99.60
Purchase #6	$229.63	11.801%	$256.7286	$256.73	$256.75	$256.70
Purchase #7	$64.98	9.639%	$71.2434	$71.24	$71.25	$71.20
7 purchase totals =	$1,027.07		$1,114.7682	$1,114.76	$1,114.75	$1,114.80