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	$173.69	11.553%	$193.7564	$193.76	$193.75	$193.80
Purchase #2	$149.32	4.174%	$155.5526	$155.55	$155.55	$155.60
Purchase #3	$141.38	12.712%	$159.3522	$159.35	$159.35	$159.40
Purchase #4	$27.84	6.393%	$29.6198	$29.62	$29.60	$29.60
Purchase #5	$172.77	13.517%	$196.1233	$196.12	$196.10	$196.10
Purchase #6	$105.45	6.126%	$111.9099	$111.91	$111.90	$111.90
Purchase #7	$22.50	11.202%	$25.0205	$25.02	$25.00	$25.00
7 purchase totals =	$792.95		$871.3347	$871.33	$871.25	$871.40