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	$78.71	13.368%	$89.232	$89.23	$89.25	$89.20
Purchase #2	$20.48	6.758%	$21.864	$21.86	$21.85	$21.90
Purchase #3	$67.32	4.637%	$70.4416	$70.44	$70.45	$70.40
Purchase #4	$62.78	11.676%	$70.1102	$70.11	$70.10	$70.10
Purchase #5	$25.94	8.222%	$28.0728	$28.07	$28.05	$28.10
Purchase #6	$176.72	4.421%	$184.5328	$184.53	$184.55	$184.50
Purchase #7	$179.28	13.614%	$203.6872	$203.69	$203.70	$203.70
7 purchase totals =	$611.23		$667.9406	$667.93	$667.95	$667.90