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	$43.98	9.640%	$48.2197	$48.22	$48.20	$48.20
Purchase #2	$68.86	13.739%	$78.3207	$78.32	$78.30	$78.30
Purchase #3	$238.49	3.664%	$247.2283	$247.23	$247.25	$247.20
Purchase #4	$185.83	12.620%	$209.2817	$209.28	$209.30	$209.30
Purchase #5	$110.62	8.229%	$119.7229	$119.72	$119.70	$119.70
Purchase #6	$83.47	11.784%	$93.3061	$93.31	$93.30	$93.30
Purchase #7	$195.47	13.523%	$221.9034	$221.90	$221.90	$221.90
7 purchase totals =	$926.72		$1,017.9828	$1,017.98	$1,017.95	$1,017.90