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	$72.83	12.796%	$82.1493	$82.15	$82.15	$82.10
Purchase #2	$71.92	4.112%	$74.8774	$74.88	$74.90	$74.90
Purchase #3	$210.58	11.861%	$235.5569	$235.56	$235.55	$235.60
Purchase #4	$238.62	4.313%	$248.9117	$248.91	$248.90	$248.90
Purchase #5	$97.30	3.138%	$100.3533	$100.35	$100.35	$100.40
Purchase #6	$169.84	10.218%	$187.1943	$187.19	$187.20	$187.20
Purchase #7	$101.25	11.528%	$112.9221	$112.92	$112.90	$112.90
7 purchase totals =	$962.34		$1,041.9650	$1,041.96	$1,041.95	$1,042.00