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	$88.91	3.850%	$92.333	$92.33	$92.35	$92.30
Purchase #2	$61.51	10.319%	$67.8572	$67.86	$67.85	$67.90
Purchase #3	$38.67	4.308%	$40.3359	$40.34	$40.35	$40.30
Purchase #4	$144.89	11.119%	$161.0003	$161.00	$161.00	$161.00
Purchase #5	$18.55	11.815%	$20.7417	$20.74	$20.75	$20.70
Purchase #6	$231.72	11.711%	$258.8567	$258.86	$258.85	$258.90
Purchase #7	$16.87	13.728%	$19.1859	$19.19	$19.20	$19.20
7 purchase totals =	$601.12		$660.3107	$660.32	$660.35	$660.30