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	$200.64	11.417%	$223.5471	$223.55	$223.55	$223.50
Purchase #2	$33.38	3.778%	$34.6411	$34.64	$34.65	$34.60
Purchase #3	$103.54	11.478%	$115.4243	$115.42	$115.40	$115.40
Purchase #4	$239.56	5.369%	$252.422	$252.42	$252.40	$252.40
Purchase #5	$224.67	13.675%	$255.3936	$255.39	$255.40	$255.40
Purchase #6	$45.73	4.502%	$47.7888	$47.79	$47.80	$47.80
Purchase #7	$80.33	11.676%	$89.7093	$89.71	$89.70	$89.70
7 purchase totals =	$927.85		$1,018.9262	$1,018.92	$1,018.90	$1,018.80