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	$63.48	12.809%	$71.6112	$71.61	$71.60	$71.60
Purchase #2	$216.75	8.702%	$235.6116	$235.61	$235.60	$235.60
Purchase #3	$155.87	3.176%	$160.8204	$160.82	$160.80	$160.80
Purchase #4	$75.30	10.654%	$83.3225	$83.32	$83.30	$83.30
Purchase #5	$37.62	12.623%	$42.3688	$42.37	$42.35	$42.40
Purchase #6	$35.46	6.306%	$37.6961	$37.70	$37.70	$37.70
Purchase #7	$197.34	3.873%	$204.983	$204.98	$205.00	$205.00
7 purchase totals =	$781.82		$836.4136	$836.41	$836.35	$836.40