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	$148.82	3.635%	$154.2296	$154.23	$154.25	$154.20
Purchase #2	$18.96	13.793%	$21.5752	$21.58	$21.60	$21.60
Purchase #3	$242.30	3.441%	$250.6375	$250.64	$250.65	$250.60
Purchase #4	$216.51	5.610%	$228.6562	$228.66	$228.65	$228.70
Purchase #5	$99.79	6.870%	$106.6456	$106.65	$106.65	$106.60
Purchase #6	$158.46	6.380%	$168.5697	$168.57	$168.55	$168.60
Purchase #7	$123.34	8.781%	$134.1705	$134.17	$134.15	$134.20
7 purchase totals =	$1,008.18		$1,064.4843	$1,064.50	$1,064.50	$1,064.50