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	$208.83	4.466%	$218.1563	$218.16	$218.15	$218.20
Purchase #2	$150.77	11.286%	$167.7859	$167.79	$167.80	$167.80
Purchase #3	$231.91	4.480%	$242.2996	$242.30	$242.30	$242.30
Purchase #4	$173.81	6.360%	$184.8643	$184.86	$184.85	$184.90
Purchase #5	$239.51	13.470%	$271.772	$271.77	$271.75	$271.80
Purchase #6	$111.46	13.321%	$126.3076	$126.31	$126.30	$126.30
Purchase #7	$153.50	9.804%	$168.5491	$168.55	$168.55	$168.50
7 purchase totals =	$1,269.79		$1,379.7348	$1,379.74	$1,379.70	$1,379.80