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	$233.83	7.385%	$251.0983	$251.10	$251.10	$251.10
Purchase #2	$165.37	11.102%	$183.7294	$183.73	$183.75	$183.70
Purchase #3	$49.70	9.555%	$54.4488	$54.45	$54.45	$54.40
Purchase #4	$50.79	7.296%	$54.4956	$54.50	$54.50	$54.50
Purchase #5	$102.93	3.787%	$106.828	$106.83	$106.85	$106.80
Purchase #6	$59.38	13.728%	$67.5317	$67.53	$67.55	$67.50
Purchase #7	$234.93	6.612%	$250.4636	$250.46	$250.45	$250.50
7 purchase totals =	$896.93		$968.5954	$968.60	$968.65	$968.50