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	$109.63	12.223%	$123.0301	$123.03	$123.05	$123.00
Purchase #2	$249.65	10.324%	$275.4239	$275.42	$275.40	$275.40
Purchase #3	$194.40	11.642%	$217.032	$217.03	$217.05	$217.00
Purchase #4	$71.42	11.337%	$79.5169	$79.52	$79.50	$79.50
Purchase #5	$92.32	4.723%	$96.6803	$96.68	$96.70	$96.70
Purchase #6	$213.29	5.871%	$225.8123	$225.81	$225.80	$225.80
Purchase #7	$90.26	11.374%	$100.5262	$100.53	$100.55	$100.50
7 purchase totals =	$1,020.97		$1,118.0217	$1,118.02	$1,118.05	$1,117.90