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	$155.78	7.718%	$167.8031	$167.80	$167.80	$167.80
Purchase #2	$133.45	5.806%	$141.1981	$141.20	$141.20	$141.20
Purchase #3	$195.69	12.864%	$220.8636	$220.86	$220.85	$220.90
Purchase #4	$220.76	5.755%	$233.4647	$233.46	$233.45	$233.50
Purchase #5	$123.74	6.600%	$131.9068	$131.91	$131.90	$131.90
Purchase #6	$132.51	11.696%	$148.0084	$148.01	$148.00	$148.00
Purchase #7	$92.62	7.118%	$99.2127	$99.21	$99.20	$99.20
7 purchase totals =	$1,054.55		$1,142.4574	$1,142.45	$1,142.40	$1,142.50