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	$62.78	4.709%	$65.7363	$65.74	$65.75	$65.70
Purchase #2	$234.76	8.747%	$255.2945	$255.29	$255.30	$255.30
Purchase #3	$115.54	10.630%	$127.8219	$127.82	$127.80	$127.80
Purchase #4	$250.39	13.652%	$284.5732	$284.57	$284.55	$284.60
Purchase #5	$180.62	3.251%	$186.492	$186.49	$186.50	$186.50
Purchase #6	$139.26	4.728%	$145.8442	$145.84	$145.85	$145.80
Purchase #7	$160.85	11.842%	$179.8979	$179.90	$179.90	$179.90
7 purchase totals =	$1,144.20		$1,245.6600	$1,245.65	$1,245.65	$1,245.60