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	$157.67	8.486%	$171.0499	$171.05	$171.05	$171.00
Purchase #2	$159.38	7.636%	$171.5503	$171.55	$171.55	$171.60
Purchase #3	$187.50	6.122%	$198.9788	$198.98	$199.00	$199.00
Purchase #4	$172.75	13.249%	$195.6376	$195.64	$195.65	$195.60
Purchase #5	$163.33	5.731%	$172.6904	$172.69	$172.70	$172.70
Purchase #6	$110.61	9.810%	$121.4608	$121.46	$121.45	$121.50
Purchase #7	$54.59	9.487%	$59.769	$59.77	$59.75	$59.80
7 purchase totals =	$1,005.83		$1,091.1368	$1,091.14	$1,091.15	$1,091.20