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	$71.76	3.182%	$74.0434	$74.04	$74.05	$74.00
Purchase #2	$171.85	4.231%	$179.121	$179.12	$179.10	$179.10
Purchase #3	$79.93	13.320%	$90.5767	$90.58	$90.60	$90.60
Purchase #4	$243.59	9.820%	$267.5105	$267.51	$267.50	$267.50
Purchase #5	$89.80	3.332%	$92.7921	$92.79	$92.80	$92.80
Purchase #6	$59.88	8.690%	$65.0836	$65.08	$65.10	$65.10
Purchase #7	$127.92	11.436%	$142.5489	$142.55	$142.55	$142.50
7 purchase totals =	$844.73		$911.6762	$911.67	$911.70	$911.60