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	$237.80	4.463%	$248.413	$248.41	$248.40	$248.40
Purchase #2	$73.89	13.613%	$83.9486	$83.95	$83.95	$83.90
Purchase #3	$207.27	7.333%	$222.4691	$222.47	$222.45	$222.50
Purchase #4	$206.91	6.196%	$219.7301	$219.73	$219.75	$219.70
Purchase #5	$77.46	7.309%	$83.1216	$83.12	$83.10	$83.10
Purchase #6	$35.50	9.464%	$38.8597	$38.86	$38.85	$38.90
Purchase #7	$32.78	9.872%	$36.016	$36.02	$36.00	$36.00
7 purchase totals =	$871.61		$932.5581	$932.56	$932.50	$932.50