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	$114.56	7.444%	$123.0878	$123.09	$123.10	$123.10
Purchase #2	$191.54	12.591%	$215.6568	$215.66	$215.65	$215.70
Purchase #3	$89.72	11.344%	$99.8978	$99.90	$99.90	$99.90
Purchase #4	$13.69	10.190%	$15.085	$15.09	$15.10	$15.10
Purchase #5	$217.45	7.158%	$233.0151	$233.02	$233.00	$233.00
Purchase #6	$169.58	7.834%	$182.8649	$182.86	$182.85	$182.90
Purchase #7	$135.98	9.684%	$149.1483	$149.15	$149.15	$149.10
7 purchase totals =	$932.52		$1,018.7557	$1,018.77	$1,018.75	$1,018.80