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	$161.95	10.387%	$178.7717	$178.77	$178.75	$178.80
Purchase #2	$230.39	4.451%	$240.6447	$240.64	$240.65	$240.60
Purchase #3	$137.59	11.444%	$153.3358	$153.34	$153.35	$153.30
Purchase #4	$89.30	12.153%	$100.1526	$100.15	$100.15	$100.20
Purchase #5	$152.64	10.223%	$168.2444	$168.24	$168.25	$168.20
Purchase #6	$250.30	13.263%	$283.4973	$283.50	$283.50	$283.50
Purchase #7	$150.31	13.829%	$171.0964	$171.10	$171.10	$171.10
7 purchase totals =	$1,172.48		$1,295.7429	$1,295.74	$1,295.75	$1,295.70