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	$85.77	6.658%	$91.4806	$91.48	$91.50	$91.50
Purchase #2	$48.27	13.146%	$54.6156	$54.62	$54.60	$54.60
Purchase #3	$30.44	12.111%	$34.1266	$34.13	$34.15	$34.10
Purchase #4	$17.64	9.352%	$19.2897	$19.29	$19.30	$19.30
Purchase #5	$73.70	3.795%	$76.4969	$76.50	$76.50	$76.50
Purchase #6	$198.36	6.441%	$211.1364	$211.14	$211.15	$211.10
Purchase #7	$151.32	11.175%	$168.23	$168.23	$168.25	$168.20
7 purchase totals =	$605.50		$655.3758	$655.39	$655.45	$655.30