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	$17.26	12.282%	$19.3799	$19.38	$19.40	$19.40
Purchase #2	$17.61	7.609%	$18.9499	$18.95	$18.95	$18.90
Purchase #3	$85.34	11.446%	$95.108	$95.11	$95.10	$95.10
Purchase #4	$139.40	4.660%	$145.896	$145.90	$145.90	$145.90
Purchase #5	$108.60	13.352%	$123.1003	$123.10	$123.10	$123.10
Purchase #6	$89.54	7.446%	$96.2071	$96.21	$96.20	$96.20
Purchase #7	$238.92	12.568%	$268.9475	$268.95	$268.95	$268.90
7 purchase totals =	$696.67		$767.5887	$767.60	$767.60	$767.50