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	$197.36	11.657%	$220.3663	$220.37	$220.35	$220.40
Purchase #2	$113.45	8.186%	$122.737	$122.74	$122.75	$122.70
Purchase #3	$105.35	6.156%	$111.8353	$111.84	$111.85	$111.80
Purchase #4	$61.36	6.421%	$65.2999	$65.30	$65.30	$65.30
Purchase #5	$233.48	12.355%	$262.3265	$262.33	$262.35	$262.30
Purchase #6	$56.36	9.236%	$61.5654	$61.57	$61.55	$61.60
Purchase #7	$72.55	8.148%	$78.4614	$78.46	$78.45	$78.50
7 purchase totals =	$839.91		$922.5918	$922.61	$922.60	$922.60