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	$226.99	4.314%	$236.7823	$236.78	$236.80	$236.80
Purchase #2	$160.70	9.823%	$176.4856	$176.49	$176.50	$176.50
Purchase #3	$90.39	9.645%	$99.1081	$99.11	$99.10	$99.10
Purchase #4	$54.48	3.332%	$56.2953	$56.30	$56.30	$56.30
Purchase #5	$161.61	8.710%	$175.6862	$175.69	$175.70	$175.70
Purchase #6	$160.60	5.142%	$168.8581	$168.86	$168.85	$168.90
Purchase #7	$161.90	10.730%	$179.2719	$179.27	$179.25	$179.30
7 purchase totals =	$1,016.67		$1,092.4875	$1,092.50	$1,092.50	$1,092.60