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	$35.54	5.681%	$37.559	$37.56	$37.55	$37.60
Purchase #2	$58.71	3.419%	$60.7173	$60.72	$60.70	$60.70
Purchase #3	$6.93	13.398%	$7.8585	$7.86	$7.85	$7.90
Purchase #4	$133.72	8.422%	$144.9819	$144.98	$145.00	$145.00
Purchase #5	$148.55	11.188%	$165.1698	$165.17	$165.15	$165.20
Purchase #6	$45.98	12.383%	$51.6737	$51.67	$51.65	$51.70
Purchase #7	$195.90	11.762%	$218.9418	$218.94	$218.95	$218.90
7 purchase totals =	$625.33		$686.9020	$686.90	$686.85	$687.00