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	$165.84	4.401%	$173.1386	$173.14	$173.15	$173.10
Purchase #2	$127.50	4.242%	$132.9086	$132.91	$132.90	$132.90
Purchase #3	$94.48	6.180%	$100.3189	$100.32	$100.30	$100.30
Purchase #4	$166.41	10.823%	$184.4206	$184.42	$184.40	$184.40
Purchase #5	$234.69	9.773%	$257.6263	$257.63	$257.65	$257.60
Purchase #6	$113.53	6.555%	$120.9719	$120.97	$120.95	$121.00
Purchase #7	$40.51	5.450%	$42.7178	$42.72	$42.70	$42.70
7 purchase totals =	$942.96		$1,012.1027	$1,012.11	$1,012.05	$1,012.00