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	$174.91	5.442%	$184.4286	$184.43	$184.45	$184.40
Purchase #2	$88.53	12.830%	$99.8884	$99.89	$99.90	$99.90
Purchase #3	$53.41	10.701%	$59.1254	$59.13	$59.15	$59.10
Purchase #4	$142.27	9.851%	$156.285	$156.29	$156.30	$156.30
Purchase #5	$12.46	4.593%	$13.0323	$13.03	$13.05	$13.00
Purchase #6	$192.36	9.637%	$210.8977	$210.90	$210.90	$210.90
Purchase #7	$189.32	11.228%	$210.5768	$210.58	$210.60	$210.60
7 purchase totals =	$853.26		$934.2342	$934.25	$934.35	$934.20