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	$28.90	12.874%	$32.6206	$32.62	$32.60	$32.60
Purchase #2	$147.37	10.438%	$162.7525	$162.75	$162.75	$162.80
Purchase #3	$163.34	4.873%	$171.2996	$171.30	$171.30	$171.30
Purchase #4	$99.81	5.362%	$105.1618	$105.16	$105.15	$105.20
Purchase #5	$222.31	8.801%	$241.8755	$241.88	$241.90	$241.90
Purchase #6	$149.37	7.102%	$159.9783	$159.98	$160.00	$160.00
Purchase #7	$211.26	5.593%	$223.0758	$223.08	$223.10	$223.10
7 purchase totals =	$1,022.36		$1,096.7641	$1,096.77	$1,096.80	$1,096.90