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	$175.59	10.155%	$193.4212	$193.42	$193.40	$193.40
Purchase #2	$190.39	5.301%	$200.4826	$200.48	$200.50	$200.50
Purchase #3	$90.98	10.709%	$100.723	$100.72	$100.70	$100.70
Purchase #4	$75.36	7.335%	$80.8877	$80.89	$80.90	$80.90
Purchase #5	$71.87	13.619%	$81.658	$81.66	$81.65	$81.70
Purchase #6	$153.99	3.860%	$159.934	$159.93	$159.95	$159.90
Purchase #7	$170.61	13.225%	$193.1732	$193.17	$193.15	$193.20
7 purchase totals =	$928.79		$1,010.2797	$1,010.27	$1,010.25	$1,010.30