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	$181.72	5.255%	$191.2694	$191.27	$191.25	$191.30
Purchase #2	$162.95	5.587%	$172.054	$172.05	$172.05	$172.10
Purchase #3	$74.29	11.488%	$82.8244	$82.82	$82.80	$82.80
Purchase #4	$42.32	7.482%	$45.4864	$45.49	$45.50	$45.50
Purchase #5	$152.56	7.145%	$163.4604	$163.46	$163.45	$163.50
Purchase #6	$224.88	4.756%	$235.5753	$235.58	$235.60	$235.60
Purchase #7	$112.76	8.807%	$122.6908	$122.69	$122.70	$122.70
7 purchase totals =	$951.48		$1,013.3607	$1,013.36	$1,013.35	$1,013.50