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	$47.80	8.285%	$51.7602	$51.76	$51.75	$51.80
Purchase #2	$133.59	12.731%	$150.5973	$150.60	$150.60	$150.60
Purchase #3	$115.45	13.142%	$130.6224	$130.62	$130.60	$130.60
Purchase #4	$67.46	7.671%	$72.6349	$72.63	$72.65	$72.60
Purchase #5	$168.79	12.800%	$190.3951	$190.40	$190.40	$190.40
Purchase #6	$193.26	8.400%	$209.4938	$209.49	$209.50	$209.50
Purchase #7	$55.71	3.104%	$57.4392	$57.44	$57.45	$57.40
7 purchase totals =	$782.06		$862.9429	$862.94	$862.95	$862.90