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	$141.35	4.776%	$148.1009	$148.10	$148.10	$148.10
Purchase #2	$19.65	10.744%	$21.7612	$21.76	$21.75	$21.80
Purchase #3	$69.27	13.435%	$78.5764	$78.58	$78.60	$78.60
Purchase #4	$224.27	8.511%	$243.3576	$243.36	$243.35	$243.40
Purchase #5	$204.68	8.527%	$222.1331	$222.13	$222.15	$222.10
Purchase #6	$204.46	9.690%	$224.2722	$224.27	$224.25	$224.30
Purchase #7	$85.49	12.716%	$96.3609	$96.36	$96.35	$96.40
7 purchase totals =	$949.17		$1,034.5623	$1,034.56	$1,034.55	$1,034.70