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	$151.25	3.447%	$156.4636	$156.46	$156.45	$156.50
Purchase #2	$197.65	8.197%	$213.8514	$213.85	$213.85	$213.90
Purchase #3	$50.31	6.239%	$53.4488	$53.45	$53.45	$53.40
Purchase #4	$208.38	5.728%	$220.316	$220.32	$220.30	$220.30
Purchase #5	$191.96	9.860%	$210.8873	$210.89	$210.90	$210.90
Purchase #6	$39.84	13.388%	$45.1738	$45.17	$45.15	$45.20
Purchase #7	$53.73	10.156%	$59.1868	$59.19	$59.20	$59.20
7 purchase totals =	$893.12		$959.3277	$959.33	$959.30	$959.40