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	$237.35	4.686%	$248.4722	$248.47	$248.45	$248.50
Purchase #2	$90.73	3.290%	$93.715	$93.72	$93.70	$93.70
Purchase #3	$173.90	10.350%	$191.8987	$191.90	$191.90	$191.90
Purchase #4	$33.30	7.169%	$35.6873	$35.69	$35.70	$35.70
Purchase #5	$213.92	12.399%	$240.4439	$240.44	$240.45	$240.40
Purchase #6	$72.45	3.426%	$74.9321	$74.93	$74.95	$74.90
Purchase #7	$115.79	13.308%	$131.1993	$131.20	$131.20	$131.20
7 purchase totals =	$937.44		$1,016.3485	$1,016.35	$1,016.35	$1,016.30