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	$95.76	8.567%	$103.9638	$103.96	$103.95	$104.00
Purchase #2	$150.76	10.640%	$166.8009	$166.80	$166.80	$166.80
Purchase #3	$158.46	4.718%	$165.9361	$165.94	$165.95	$165.90
Purchase #4	$147.42	3.196%	$152.1315	$152.13	$152.15	$152.10
Purchase #5	$159.44	3.754%	$165.4254	$165.43	$165.45	$165.40
Purchase #6	$168.55	4.167%	$175.5735	$175.57	$175.55	$175.60
Purchase #7	$68.27	12.151%	$76.5655	$76.57	$76.55	$76.60
7 purchase totals =	$948.66		$1,006.3967	$1,006.40	$1,006.40	$1,006.40