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	$198.77	9.779%	$218.2077	$218.21	$218.20	$218.20
Purchase #2	$209.63	6.677%	$223.627	$223.63	$223.65	$223.60
Purchase #3	$215.26	3.356%	$222.4841	$222.48	$222.50	$222.50
Purchase #4	$165.57	12.762%	$186.7	$186.70	$186.70	$186.70
Purchase #5	$44.27	10.138%	$48.7581	$48.76	$48.75	$48.80
Purchase #6	$51.54	7.817%	$55.5689	$55.57	$55.55	$55.60
Purchase #7	$74.34	5.281%	$78.2659	$78.27	$78.25	$78.30
7 purchase totals =	$959.38		$1,033.6117	$1,033.62	$1,033.60	$1,033.70