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	$120.60	11.196%	$134.1024	$134.10	$134.10	$134.10
Purchase #2	$36.98	11.717%	$41.3129	$41.31	$41.30	$41.30
Purchase #3	$165.86	4.207%	$172.8377	$172.84	$172.85	$172.80
Purchase #4	$185.58	7.707%	$199.8827	$199.88	$199.90	$199.90
Purchase #5	$39.98	6.250%	$42.4788	$42.48	$42.50	$42.50
Purchase #6	$162.55	5.623%	$171.6902	$171.69	$171.70	$171.70
Purchase #7	$38.79	8.271%	$41.9983	$42.00	$42.00	$42.00
7 purchase totals =	$750.34		$804.3030	$804.30	$804.35	$804.30