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	$52.45	13.121%	$59.332	$59.33	$59.35	$59.30
Purchase #2	$212.56	5.394%	$224.0255	$224.03	$224.05	$224.00
Purchase #3	$19.84	4.572%	$20.7471	$20.75	$20.75	$20.70
Purchase #4	$64.44	4.619%	$67.4165	$67.42	$67.40	$67.40
Purchase #5	$82.74	8.316%	$89.6207	$89.62	$89.60	$89.60
Purchase #6	$135.76	3.764%	$140.87	$140.87	$140.85	$140.90
Purchase #7	$112.76	4.488%	$117.8207	$117.82	$117.80	$117.80
7 purchase totals =	$680.55		$719.8325	$719.84	$719.80	$719.70