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	$219.81	3.557%	$227.6286	$227.63	$227.65	$227.60
Purchase #2	$98.37	3.465%	$101.7785	$101.78	$101.80	$101.80
Purchase #3	$111.65	11.168%	$124.1191	$124.12	$124.10	$124.10
Purchase #4	$210.43	3.650%	$218.1107	$218.11	$218.10	$218.10
Purchase #5	$129.64	11.717%	$144.8299	$144.83	$144.85	$144.80
Purchase #6	$118.84	3.733%	$123.2763	$123.28	$123.30	$123.30
Purchase #7	$47.59	10.389%	$52.5341	$52.53	$52.55	$52.50
7 purchase totals =	$936.33		$992.2772	$992.28	$992.35	$992.20