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	$168.79	9.361%	$184.5904	$184.59	$184.60	$184.60
Purchase #2	$218.46	7.310%	$234.4294	$234.43	$234.45	$234.40
Purchase #3	$110.85	12.749%	$124.9823	$124.98	$125.00	$125.00
Purchase #4	$156.79	10.253%	$172.8657	$172.87	$172.85	$172.90
Purchase #5	$98.75	4.772%	$103.4624	$103.46	$103.45	$103.50
Purchase #6	$111.86	4.781%	$117.208	$117.21	$117.20	$117.20
Purchase #7	$175.34	10.466%	$193.6911	$193.69	$193.70	$193.70
7 purchase totals =	$1,040.84		$1,131.2293	$1,131.23	$1,131.25	$1,131.30