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	$232.41	13.342%	$263.4181	$263.42	$263.40	$263.40
Purchase #2	$145.61	5.361%	$153.4162	$153.42	$153.40	$153.40
Purchase #3	$58.44	6.557%	$62.2719	$62.27	$62.25	$62.30
Purchase #4	$34.36	9.690%	$37.6895	$37.69	$37.70	$37.70
Purchase #5	$32.34	11.835%	$36.1674	$36.17	$36.15	$36.20
Purchase #6	$31.81	3.216%	$32.833	$32.83	$32.85	$32.80
Purchase #7	$110.63	8.257%	$119.7647	$119.76	$119.75	$119.80
7 purchase totals =	$645.60		$705.5608	$705.56	$705.50	$705.60