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	$224.62	13.236%	$254.3507	$254.35	$254.35	$254.40
Purchase #2	$59.74	9.323%	$65.3096	$65.31	$65.30	$65.30
Purchase #3	$126.28	11.737%	$141.1015	$141.10	$141.10	$141.10
Purchase #4	$125.78	10.465%	$138.9429	$138.94	$138.95	$138.90
Purchase #5	$79.86	13.845%	$90.9166	$90.92	$90.90	$90.90
Purchase #6	$213.66	13.598%	$242.7135	$242.71	$242.70	$242.70
Purchase #7	$125.34	4.425%	$130.8863	$130.89	$130.90	$130.90
7 purchase totals =	$955.28		$1,064.2211	$1,064.22	$1,064.20	$1,064.20