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	$13.87	4.665%	$14.517	$14.52	$14.50	$14.50
Purchase #2	$207.33	4.428%	$216.5106	$216.51	$216.50	$216.50
Purchase #3	$51.86	13.791%	$59.012	$59.01	$59.00	$59.00
Purchase #4	$65.79	11.682%	$73.4756	$73.48	$73.50	$73.50
Purchase #5	$64.29	6.238%	$68.3004	$68.30	$68.30	$68.30
Purchase #6	$76.97	7.425%	$82.685	$82.69	$82.70	$82.70
Purchase #7	$6.61	3.145%	$6.8179	$6.82	$6.80	$6.80
7 purchase totals =	$486.72		$521.3185	$521.33	$521.30	$521.30