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	$123.57	5.675%	$130.5826	$130.58	$130.60	$130.60
Purchase #2	$225.27	13.845%	$256.4586	$256.46	$256.45	$256.50
Purchase #3	$20.80	13.654%	$23.64	$23.64	$23.65	$23.60
Purchase #4	$229.73	12.542%	$258.5427	$258.54	$258.55	$258.50
Purchase #5	$20.45	4.374%	$21.3445	$21.34	$21.35	$21.30
Purchase #6	$209.72	11.248%	$233.3093	$233.31	$233.30	$233.30
Purchase #7	$232.69	13.272%	$263.5726	$263.57	$263.55	$263.60
7 purchase totals =	$1,062.23		$1,187.4503	$1,187.44	$1,187.45	$1,187.40