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	$101.41	5.150%	$106.6326	$106.63	$106.65	$106.60
Purchase #2	$180.83	5.647%	$191.0415	$191.04	$191.05	$191.00
Purchase #3	$157.33	5.231%	$165.5599	$165.56	$165.55	$165.60
Purchase #4	$42.53	6.593%	$45.334	$45.33	$45.35	$45.30
Purchase #5	$222.59	9.202%	$243.0727	$243.07	$243.05	$243.10
Purchase #6	$59.86	13.252%	$67.7926	$67.79	$67.80	$67.80
Purchase #7	$47.78	11.265%	$53.1624	$53.16	$53.15	$53.20
7 purchase totals =	$812.33		$872.5957	$872.58	$872.60	$872.60