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	$115.61	11.422%	$128.815	$128.82	$128.80	$128.80
Purchase #2	$25.84	11.556%	$28.8261	$28.83	$28.85	$28.80
Purchase #3	$41.78	13.744%	$47.5222	$47.52	$47.50	$47.50
Purchase #4	$183.79	5.275%	$193.4849	$193.48	$193.50	$193.50
Purchase #5	$172.96	7.508%	$185.9458	$185.95	$185.95	$185.90
Purchase #6	$219.27	8.519%	$237.9496	$237.95	$237.95	$237.90
Purchase #7	$243.76	11.387%	$271.517	$271.52	$271.50	$271.50
7 purchase totals =	$1,003.01		$1,094.0606	$1,094.07	$1,094.05	$1,093.90