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	$116.42	3.261%	$120.2165	$120.22	$120.20	$120.20
Purchase #2	$190.27	5.147%	$200.0632	$200.06	$200.05	$200.10
Purchase #3	$38.44	6.787%	$41.0489	$41.05	$41.05	$41.00
Purchase #4	$167.93	8.584%	$182.3451	$182.35	$182.35	$182.30
Purchase #5	$118.60	4.668%	$124.1362	$124.14	$124.15	$124.10
Purchase #6	$165.64	4.738%	$173.488	$173.49	$173.50	$173.50
Purchase #7	$94.97	5.379%	$100.0784	$100.08	$100.10	$100.10
7 purchase totals =	$892.27		$941.3763	$941.39	$941.40	$941.30