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	$67.86	12.371%	$76.255	$76.26	$76.25	$76.30
Purchase #2	$38.65	9.498%	$42.321	$42.32	$42.30	$42.30
Purchase #3	$189.55	3.496%	$196.1767	$196.18	$196.20	$196.20
Purchase #4	$170.52	6.466%	$181.5458	$181.55	$181.55	$181.50
Purchase #5	$171.51	7.166%	$183.8004	$183.80	$183.80	$183.80
Purchase #6	$182.65	3.323%	$188.7195	$188.72	$188.70	$188.70
Purchase #7	$187.75	6.578%	$200.1002	$200.10	$200.10	$200.10
7 purchase totals =	$1,008.49		$1,068.9186	$1,068.93	$1,068.90	$1,068.90