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	$104.79	6.769%	$111.8832	$111.88	$111.90	$111.90
Purchase #2	$96.68	6.750%	$103.2059	$103.21	$103.20	$103.20
Purchase #3	$143.56	9.585%	$157.3202	$157.32	$157.30	$157.30
Purchase #4	$69.75	11.147%	$77.525	$77.53	$77.55	$77.50
Purchase #5	$110.41	3.382%	$114.1441	$114.14	$114.15	$114.10
Purchase #6	$48.28	3.318%	$49.8819	$49.88	$49.90	$49.90
Purchase #7	$131.62	11.359%	$146.5707	$146.57	$146.55	$146.60
7 purchase totals =	$705.09		$760.5310	$760.53	$760.55	$760.50