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	$65.55	9.563%	$71.8185	$71.82	$71.80	$71.80
Purchase #2	$151.25	6.134%	$160.5277	$160.53	$160.55	$160.50
Purchase #3	$86.36	3.135%	$89.0674	$89.07	$89.05	$89.10
Purchase #4	$101.62	13.661%	$115.5023	$115.50	$115.50	$115.50
Purchase #5	$175.77	12.356%	$197.4881	$197.49	$197.50	$197.50
Purchase #6	$47.25	13.358%	$53.5617	$53.56	$53.55	$53.60
Purchase #7	$85.57	11.507%	$95.4165	$95.42	$95.40	$95.40
7 purchase totals =	$713.37		$783.3822	$783.39	$783.35	$783.40