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	$63.52	13.133%	$71.8621	$71.86	$71.85	$71.90
Purchase #2	$168.73	9.674%	$185.0529	$185.05	$185.05	$185.10
Purchase #3	$171.25	9.646%	$187.7688	$187.77	$187.75	$187.80
Purchase #4	$202.81	6.715%	$216.4287	$216.43	$216.45	$216.40
Purchase #5	$91.82	9.656%	$100.6861	$100.69	$100.70	$100.70
Purchase #6	$96.38	4.850%	$101.0544	$101.05	$101.05	$101.10
Purchase #7	$37.61	4.840%	$39.4303	$39.43	$39.45	$39.40
7 purchase totals =	$832.12		$902.2833	$902.28	$902.30	$902.40