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	$195.30	9.402%	$213.6621	$213.66	$213.65	$213.70
Purchase #2	$56.27	5.120%	$59.151	$59.15	$59.15	$59.20
Purchase #3	$217.75	9.530%	$238.5016	$238.50	$238.50	$238.50
Purchase #4	$133.43	8.864%	$145.2572	$145.26	$145.25	$145.30
Purchase #5	$69.89	3.381%	$72.253	$72.25	$72.25	$72.30
Purchase #6	$121.61	6.421%	$129.4186	$129.42	$129.40	$129.40
Purchase #7	$40.86	11.174%	$45.4257	$45.43	$45.45	$45.40
7 purchase totals =	$835.11		$903.6692	$903.67	$903.65	$903.80