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	$227.83	11.839%	$254.8028	$254.80	$254.80	$254.80
Purchase #2	$153.73	12.107%	$172.3421	$172.34	$172.35	$172.30
Purchase #3	$187.27	6.391%	$199.2384	$199.24	$199.25	$199.20
Purchase #4	$92.82	11.449%	$103.447	$103.45	$103.45	$103.40
Purchase #5	$116.76	6.855%	$124.7639	$124.76	$124.75	$124.80
Purchase #6	$49.68	11.334%	$55.3107	$55.31	$55.30	$55.30
Purchase #7	$50.48	13.464%	$57.2766	$57.28	$57.30	$57.30
7 purchase totals =	$878.57		$967.1815	$967.18	$967.20	$967.10