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	$66.35	9.483%	$72.642	$72.64	$72.65	$72.60
Purchase #2	$193.44	11.279%	$215.2581	$215.26	$215.25	$215.30
Purchase #3	$78.64	8.397%	$85.2434	$85.24	$85.25	$85.20
Purchase #4	$135.78	5.865%	$143.7435	$143.74	$143.75	$143.70
Purchase #5	$224.68	8.707%	$244.2429	$244.24	$244.25	$244.20
Purchase #6	$143.39	9.687%	$157.2802	$157.28	$157.30	$157.30
Purchase #7	$95.31	5.725%	$100.7665	$100.77	$100.75	$100.80
7 purchase totals =	$937.59		$1,019.1766	$1,019.17	$1,019.20	$1,019.10