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	$217.32	12.413%	$244.2959	$244.30	$244.30	$244.30
Purchase #2	$208.91	3.131%	$215.451	$215.45	$215.45	$215.50
Purchase #3	$55.67	13.559%	$63.2183	$63.22	$63.20	$63.20
Purchase #4	$242.35	5.173%	$254.8868	$254.89	$254.90	$254.90
Purchase #5	$248.49	6.428%	$264.4629	$264.46	$264.45	$264.50
Purchase #6	$155.95	5.232%	$164.1093	$164.11	$164.10	$164.10
Purchase #7	$179.45	4.483%	$187.4947	$187.49	$187.50	$187.50
7 purchase totals =	$1,308.14		$1,393.9189	$1,393.92	$1,393.90	$1,394.00