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	$65.37	10.137%	$71.9966	$72.00	$72.00	$72.00
Purchase #2	$167.58	12.217%	$188.0532	$188.05	$188.05	$188.10
Purchase #3	$245.26	6.702%	$261.6973	$261.70	$261.70	$261.70
Purchase #4	$23.82	11.483%	$26.5553	$26.56	$26.55	$26.60
Purchase #5	$229.37	11.366%	$255.4402	$255.44	$255.45	$255.40
Purchase #6	$80.81	10.301%	$89.1342	$89.13	$89.15	$89.10
Purchase #7	$65.61	3.228%	$67.7279	$67.73	$67.75	$67.70
7 purchase totals =	$877.82		$960.6047	$960.61	$960.65	$960.60