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	$131.30	12.648%	$147.9068	$147.91	$147.90	$147.90
Purchase #2	$237.65	13.389%	$269.469	$269.47	$269.45	$269.50
Purchase #3	$45.25	5.240%	$47.6211	$47.62	$47.60	$47.60
Purchase #4	$200.72	12.356%	$225.521	$225.52	$225.50	$225.50
Purchase #5	$104.73	5.451%	$110.4388	$110.44	$110.45	$110.40
Purchase #6	$174.50	6.512%	$185.8634	$185.86	$185.85	$185.90
Purchase #7	$209.99	8.404%	$227.6376	$227.64	$227.65	$227.60
7 purchase totals =	$1,104.14		$1,214.4577	$1,214.46	$1,214.40	$1,214.40