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	$135.40	8.143%	$146.4256	$146.43	$146.45	$146.40
Purchase #2	$244.61	7.168%	$262.1436	$262.14	$262.15	$262.10
Purchase #3	$245.37	10.792%	$271.8503	$271.85	$271.85	$271.90
Purchase #4	$112.49	3.543%	$116.4755	$116.48	$116.50	$116.50
Purchase #5	$100.53	9.263%	$109.8421	$109.84	$109.85	$109.80
Purchase #6	$6.79	10.687%	$7.5156	$7.52	$7.50	$7.50
Purchase #7	$160.28	6.550%	$170.7783	$170.78	$170.80	$170.80
7 purchase totals =	$1,005.47		$1,085.0310	$1,085.04	$1,085.10	$1,085.00