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	$221.96	5.384%	$233.9103	$233.91	$233.90	$233.90
Purchase #2	$98.49	12.784%	$111.081	$111.08	$111.10	$111.10
Purchase #3	$40.45	13.385%	$45.8642	$45.86	$45.85	$45.90
Purchase #4	$196.62	8.340%	$213.0181	$213.02	$213.00	$213.00
Purchase #5	$165.46	7.207%	$177.3847	$177.38	$177.40	$177.40
Purchase #6	$215.76	12.316%	$242.333	$242.33	$242.35	$242.30
Purchase #7	$196.30	6.678%	$209.4089	$209.41	$209.40	$209.40
7 purchase totals =	$1,135.04		$1,233.0002	$1,232.99	$1,233.00	$1,233.00