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	$207.71	4.739%	$217.5534	$217.55	$217.55	$217.60
Purchase #2	$229.64	5.742%	$242.8259	$242.83	$242.85	$242.80
Purchase #3	$107.52	10.562%	$118.8763	$118.88	$118.90	$118.90
Purchase #4	$46.72	4.240%	$48.7009	$48.70	$48.70	$48.70
Purchase #5	$184.50	5.837%	$195.2693	$195.27	$195.25	$195.30
Purchase #6	$55.39	7.201%	$59.3786	$59.38	$59.40	$59.40
Purchase #7	$85.37	5.828%	$90.3454	$90.35	$90.35	$90.30
7 purchase totals =	$916.85		$972.9498	$972.96	$973.00	$973.00