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	$29.73	13.371%	$33.7052	$33.71	$33.70	$33.70
Purchase #2	$113.44	12.555%	$127.6824	$127.68	$127.70	$127.70
Purchase #3	$233.48	4.313%	$243.55	$243.55	$243.55	$243.60
Purchase #4	$82.91	7.781%	$89.3612	$89.36	$89.35	$89.40
Purchase #5	$243.84	8.589%	$264.7834	$264.78	$264.80	$264.80
Purchase #6	$39.94	13.322%	$45.2608	$45.26	$45.25	$45.30
Purchase #7	$204.39	7.732%	$220.1934	$220.19	$220.20	$220.20
7 purchase totals =	$947.73		$1,024.5364	$1,024.53	$1,024.55	$1,024.70