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	$54.29	12.176%	$60.9004	$60.90	$60.90	$60.90
Purchase #2	$161.86	6.544%	$172.4521	$172.45	$172.45	$172.50
Purchase #3	$67.83	4.253%	$70.7148	$70.71	$70.70	$70.70
Purchase #4	$27.88	10.538%	$30.818	$30.82	$30.80	$30.80
Purchase #5	$229.65	6.465%	$244.4969	$244.50	$244.50	$244.50
Purchase #6	$153.32	10.157%	$168.8927	$168.89	$168.90	$168.90
Purchase #7	$201.54	10.843%	$223.393	$223.39	$223.40	$223.40
7 purchase totals =	$896.37		$971.6679	$971.66	$971.65	$971.70