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	$230.39	5.784%	$243.7158	$243.72	$243.70	$243.70
Purchase #2	$93.46	7.315%	$100.2966	$100.30	$100.30	$100.30
Purchase #3	$141.36	6.241%	$150.1823	$150.18	$150.20	$150.20
Purchase #4	$170.32	5.320%	$179.381	$179.38	$179.40	$179.40
Purchase #5	$177.58	13.132%	$200.8998	$200.90	$200.90	$200.90
Purchase #6	$166.58	10.722%	$184.4407	$184.44	$184.45	$184.40
Purchase #7	$44.37	11.790%	$49.6012	$49.60	$49.60	$49.60
7 purchase totals =	$1,024.06		$1,108.5174	$1,108.52	$1,108.55	$1,108.50