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	$124.39	10.629%	$137.6114	$137.61	$137.60	$137.60
Purchase #2	$230.30	5.720%	$243.4732	$243.47	$243.45	$243.50
Purchase #3	$147.68	8.530%	$160.2771	$160.28	$160.30	$160.30
Purchase #4	$181.39	10.762%	$200.9112	$200.91	$200.90	$200.90
Purchase #5	$120.43	6.325%	$128.0472	$128.05	$128.05	$128.00
Purchase #6	$134.37	13.615%	$152.6645	$152.66	$152.65	$152.70
Purchase #7	$26.85	4.159%	$27.9667	$27.97	$27.95	$28.00
7 purchase totals =	$965.41		$1,050.9513	$1,050.95	$1,050.90	$1,051.00