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	$187.33	13.865%	$213.3033	$213.30	$213.30	$213.30
Purchase #2	$112.31	10.626%	$124.2441	$124.24	$124.25	$124.20
Purchase #3	$175.62	11.752%	$196.2589	$196.26	$196.25	$196.30
Purchase #4	$106.47	4.564%	$111.3293	$111.33	$111.35	$111.30
Purchase #5	$234.49	4.662%	$245.4219	$245.42	$245.40	$245.40
Purchase #6	$151.90	8.603%	$164.968	$164.97	$164.95	$165.00
Purchase #7	$176.79	13.555%	$200.7539	$200.75	$200.75	$200.80
7 purchase totals =	$1,144.91		$1,256.2794	$1,256.27	$1,256.25	$1,256.30