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	$210.33	9.289%	$229.8676	$229.87	$229.85	$229.90
Purchase #2	$81.95	11.827%	$91.6422	$91.64	$91.65	$91.60
Purchase #3	$17.66	5.407%	$18.6149	$18.61	$18.60	$18.60
Purchase #4	$140.46	5.583%	$148.3019	$148.30	$148.30	$148.30
Purchase #5	$153.59	13.291%	$174.0036	$174.00	$174.00	$174.00
Purchase #6	$229.55	10.367%	$253.3474	$253.35	$253.35	$253.30
Purchase #7	$94.48	5.657%	$99.8247	$99.82	$99.80	$99.80
7 purchase totals =	$928.02		$1,015.6023	$1,015.59	$1,015.55	$1,015.50