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	$106.47	4.607%	$111.3751	$111.38	$111.40	$111.40
Purchase #2	$102.26	9.451%	$111.9246	$111.92	$111.90	$111.90
Purchase #3	$160.27	4.172%	$166.9565	$166.96	$166.95	$167.00
Purchase #4	$177.95	6.684%	$189.8442	$189.84	$189.85	$189.80
Purchase #5	$75.96	12.227%	$85.2476	$85.25	$85.25	$85.20
Purchase #6	$217.69	5.204%	$229.0186	$229.02	$229.00	$229.00
Purchase #7	$79.83	9.144%	$87.1297	$87.13	$87.15	$87.10
7 purchase totals =	$920.43		$981.4963	$981.50	$981.50	$981.40