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	$106.66	6.222%	$113.2964	$113.30	$113.30	$113.30
Purchase #2	$131.88	11.351%	$146.8497	$146.85	$146.85	$146.80
Purchase #3	$34.94	10.290%	$38.5353	$38.54	$38.55	$38.50
Purchase #4	$64.40	10.581%	$71.2142	$71.21	$71.20	$71.20
Purchase #5	$212.90	11.122%	$236.5787	$236.58	$236.60	$236.60
Purchase #6	$214.64	3.561%	$222.2833	$222.28	$222.30	$222.30
Purchase #7	$174.69	7.808%	$188.3298	$188.33	$188.35	$188.30
7 purchase totals =	$940.11		$1,017.0874	$1,017.09	$1,017.15	$1,017.00