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	$112.28	4.132%	$116.9194	$116.92	$116.90	$116.90
Purchase #2	$107.71	3.277%	$111.2397	$111.24	$111.25	$111.20
Purchase #3	$64.35	12.302%	$72.2663	$72.27	$72.25	$72.30
Purchase #4	$122.70	11.135%	$136.3626	$136.36	$136.35	$136.40
Purchase #5	$181.72	5.430%	$191.5874	$191.59	$191.60	$191.60
Purchase #6	$148.38	11.650%	$165.6663	$165.67	$165.65	$165.70
Purchase #7	$29.58	3.348%	$30.5703	$30.57	$30.55	$30.60
7 purchase totals =	$766.72		$824.6120	$824.62	$824.55	$824.70