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	$95.55	4.680%	$100.0217	$100.02	$100.00	$100.00
Purchase #2	$147.73	13.126%	$167.121	$167.12	$167.10	$167.10
Purchase #3	$6.27	4.784%	$6.57	$6.57	$6.55	$6.60
Purchase #4	$244.71	9.190%	$267.1988	$267.20	$267.20	$267.20
Purchase #5	$178.31	12.219%	$200.0977	$200.10	$200.10	$200.10
Purchase #6	$166.63	3.708%	$172.8086	$172.81	$172.80	$172.80
Purchase #7	$160.96	13.760%	$183.1081	$183.11	$183.10	$183.10
7 purchase totals =	$1,000.16		$1,096.9259	$1,096.93	$1,096.85	$1,096.90