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	$249.29	7.566%	$268.1513	$268.15	$268.15	$268.20
Purchase #2	$76.93	5.510%	$81.1688	$81.17	$81.15	$81.20
Purchase #3	$47.62	12.538%	$53.5906	$53.59	$53.60	$53.60
Purchase #4	$106.52	4.457%	$111.2676	$111.27	$111.25	$111.30
Purchase #5	$200.35	10.169%	$220.7236	$220.72	$220.70	$220.70
Purchase #6	$62.93	7.673%	$67.7586	$67.76	$67.75	$67.80
Purchase #7	$52.46	6.222%	$55.7241	$55.72	$55.70	$55.70
7 purchase totals =	$796.10		$858.3846	$858.38	$858.30	$858.50