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	$82.62	6.412%	$87.9176	$87.92	$87.90	$87.90
Purchase #2	$31.26	13.603%	$35.5123	$35.51	$35.50	$35.50
Purchase #3	$139.87	10.593%	$154.6864	$154.69	$154.70	$154.70
Purchase #4	$96.74	10.111%	$106.5214	$106.52	$106.50	$106.50
Purchase #5	$202.30	9.793%	$222.1112	$222.11	$222.10	$222.10
Purchase #6	$89.25	11.777%	$99.761	$99.76	$99.75	$99.80
Purchase #7	$24.49	5.859%	$25.9249	$25.92	$25.90	$25.90
7 purchase totals =	$666.53		$732.4348	$732.43	$732.35	$732.40