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	$70.77	5.131%	$74.4012	$74.40	$74.40	$74.40
Purchase #2	$99.74	9.686%	$109.4008	$109.40	$109.40	$109.40
Purchase #3	$233.40	6.180%	$247.8241	$247.82	$247.80	$247.80
Purchase #4	$154.56	8.262%	$167.3297	$167.33	$167.35	$167.30
Purchase #5	$92.40	8.515%	$100.2679	$100.27	$100.25	$100.30
Purchase #6	$238.53	7.489%	$256.3935	$256.39	$256.40	$256.40
Purchase #7	$67.66	10.162%	$74.5356	$74.54	$74.55	$74.50
7 purchase totals =	$957.06		$1,030.1528	$1,030.15	$1,030.15	$1,030.10