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	$47.28	10.642%	$52.3115	$52.31	$52.30	$52.30
Purchase #2	$227.31	11.440%	$253.3143	$253.31	$253.30	$253.30
Purchase #3	$40.86	4.837%	$42.8364	$42.84	$42.85	$42.80
Purchase #4	$10.96	9.691%	$12.0221	$12.02	$12.00	$12.00
Purchase #5	$153.69	11.755%	$171.7563	$171.76	$171.75	$171.80
Purchase #6	$26.59	10.253%	$29.3163	$29.32	$29.30	$29.30
Purchase #7	$219.56	6.625%	$234.1059	$234.11	$234.10	$234.10
7 purchase totals =	$726.25		$795.6628	$795.67	$795.60	$795.60