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	$144.44	5.385%	$152.2181	$152.22	$152.20	$152.20
Purchase #2	$24.65	9.635%	$27.025	$27.03	$27.05	$27.00
Purchase #3	$209.44	6.242%	$222.5132	$222.51	$222.50	$222.50
Purchase #4	$223.96	9.379%	$244.9652	$244.97	$244.95	$245.00
Purchase #5	$50.44	6.230%	$53.5824	$53.58	$53.60	$53.60
Purchase #6	$86.88	6.596%	$92.6106	$92.61	$92.60	$92.60
Purchase #7	$127.75	8.806%	$138.9997	$139.00	$139.00	$139.00
7 purchase totals =	$867.56		$931.9142	$931.92	$931.90	$931.90