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	$247.92	6.674%	$264.4662	$264.47	$264.45	$264.50
Purchase #2	$249.28	11.490%	$277.9223	$277.92	$277.90	$277.90
Purchase #3	$206.51	6.244%	$219.4045	$219.40	$219.40	$219.40
Purchase #4	$30.55	7.204%	$32.7508	$32.75	$32.75	$32.80
Purchase #5	$5.73	10.278%	$6.3189	$6.32	$6.30	$6.30
Purchase #6	$89.55	13.682%	$101.8022	$101.80	$101.80	$101.80
Purchase #7	$121.57	5.161%	$127.8442	$127.84	$127.85	$127.80
7 purchase totals =	$951.11		$1,030.5091	$1,030.50	$1,030.45	$1,030.50