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	$172.93	4.560%	$180.8156	$180.82	$180.80	$180.80
Purchase #2	$156.26	5.792%	$165.3106	$165.31	$165.30	$165.30
Purchase #3	$234.93	12.335%	$263.9086	$263.91	$263.90	$263.90
Purchase #4	$90.53	12.571%	$101.9105	$101.91	$101.90	$101.90
Purchase #5	$139.82	13.292%	$158.4049	$158.40	$158.40	$158.40
Purchase #6	$113.99	11.538%	$127.1422	$127.14	$127.15	$127.10
Purchase #7	$83.93	4.286%	$87.5272	$87.53	$87.55	$87.50
7 purchase totals =	$992.39		$1,085.0196	$1,085.02	$1,085.00	$1,084.90