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	$85.79	5.695%	$90.6757	$90.68	$90.70	$90.70
Purchase #2	$143.70	7.476%	$154.443	$154.44	$154.45	$154.40
Purchase #3	$133.53	8.841%	$145.3354	$145.34	$145.35	$145.30
Purchase #4	$232.79	13.759%	$264.8196	$264.82	$264.80	$264.80
Purchase #5	$76.27	4.318%	$79.5633	$79.56	$79.55	$79.60
Purchase #6	$145.62	10.735%	$161.2523	$161.25	$161.25	$161.30
Purchase #7	$119.98	6.589%	$127.8855	$127.89	$127.90	$127.90
7 purchase totals =	$937.68		$1,023.9748	$1,023.98	$1,024.00	$1,024.00