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	$18.64	5.586%	$19.6812	$19.68	$19.70	$19.70
Purchase #2	$238.45	7.564%	$256.4864	$256.49	$256.50	$256.50
Purchase #3	$53.90	3.383%	$55.7234	$55.72	$55.70	$55.70
Purchase #4	$106.86	4.230%	$111.3802	$111.38	$111.40	$111.40
Purchase #5	$18.28	4.546%	$19.111	$19.11	$19.10	$19.10
Purchase #6	$69.99	5.517%	$73.8513	$73.85	$73.85	$73.90
Purchase #7	$198.47	8.804%	$215.9433	$215.94	$215.95	$215.90
7 purchase totals =	$704.59		$752.1768	$752.17	$752.20	$752.20