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	$232.30	4.846%	$243.5573	$243.56	$243.55	$243.60
Purchase #2	$189.64	11.714%	$211.8544	$211.85	$211.85	$211.90
Purchase #3	$94.81	11.263%	$105.4885	$105.49	$105.50	$105.50
Purchase #4	$89.83	9.843%	$98.672	$98.67	$98.65	$98.70
Purchase #5	$73.90	9.801%	$81.1429	$81.14	$81.15	$81.10
Purchase #6	$173.91	11.306%	$193.5723	$193.57	$193.55	$193.60
Purchase #7	$176.93	7.174%	$189.623	$189.62	$189.60	$189.60
7 purchase totals =	$1,031.32		$1,123.9104	$1,123.90	$1,123.85	$1,124.00