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	$144.60	5.339%	$152.3202	$152.32	$152.30	$152.30
Purchase #2	$155.98	9.832%	$171.316	$171.32	$171.30	$171.30
Purchase #3	$110.83	8.485%	$120.2339	$120.23	$120.25	$120.20
Purchase #4	$53.59	10.371%	$59.1478	$59.15	$59.15	$59.10
Purchase #5	$147.40	4.255%	$153.6719	$153.67	$153.65	$153.70
Purchase #6	$189.73	5.207%	$199.6092	$199.61	$199.60	$199.60
Purchase #7	$149.42	9.690%	$163.8988	$163.90	$163.90	$163.90
7 purchase totals =	$951.55		$1,020.1978	$1,020.20	$1,020.15	$1,020.10