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	$134.65	10.790%	$149.1787	$149.18	$149.20	$149.20
Purchase #2	$153.94	7.171%	$164.979	$164.98	$165.00	$165.00
Purchase #3	$45.57	4.631%	$47.6803	$47.68	$47.70	$47.70
Purchase #4	$38.76	10.674%	$42.8972	$42.90	$42.90	$42.90
Purchase #5	$149.58	12.596%	$168.4211	$168.42	$168.40	$168.40
Purchase #6	$38.28	11.514%	$42.6876	$42.69	$42.70	$42.70
Purchase #7	$149.43	12.517%	$168.1342	$168.13	$168.15	$168.10
7 purchase totals =	$710.21		$783.9781	$783.98	$784.05	$784.00