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	$142.39	4.363%	$148.6025	$148.60	$148.60	$148.60
Purchase #2	$98.52	10.791%	$109.1513	$109.15	$109.15	$109.20
Purchase #3	$54.35	7.729%	$58.5507	$58.55	$58.55	$58.60
Purchase #4	$45.43	9.692%	$49.8331	$49.83	$49.85	$49.80
Purchase #5	$238.45	11.794%	$266.5728	$266.57	$266.55	$266.60
Purchase #6	$144.69	6.164%	$153.6087	$153.61	$153.60	$153.60
Purchase #7	$129.92	9.572%	$142.3559	$142.36	$142.35	$142.40
7 purchase totals =	$853.75		$928.6750	$928.67	$928.65	$928.80