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	$88.66	7.240%	$95.079	$95.08	$95.10	$95.10
Purchase #2	$230.90	13.817%	$262.8035	$262.80	$262.80	$262.80
Purchase #3	$55.60	3.180%	$57.3681	$57.37	$57.35	$57.40
Purchase #4	$123.38	11.486%	$137.5514	$137.55	$137.55	$137.60
Purchase #5	$238.45	13.420%	$270.45	$270.45	$270.45	$270.50
Purchase #6	$71.62	11.730%	$80.021	$80.02	$80.00	$80.00
Purchase #7	$39.92	13.409%	$45.2729	$45.27	$45.25	$45.30
7 purchase totals =	$848.53		$948.5459	$948.54	$948.50	$948.70