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	$173.86	11.696%	$194.1947	$194.19	$194.20	$194.20
Purchase #2	$247.64	10.603%	$273.8973	$273.90	$273.90	$273.90
Purchase #3	$37.40	13.497%	$42.4479	$42.45	$42.45	$42.40
Purchase #4	$143.67	11.434%	$160.0972	$160.10	$160.10	$160.10
Purchase #5	$234.44	3.616%	$242.9174	$242.92	$242.90	$242.90
Purchase #6	$226.91	8.241%	$245.6097	$245.61	$245.60	$245.60
Purchase #7	$75.86	9.735%	$83.245	$83.25	$83.25	$83.20
7 purchase totals =	$1,139.78		$1,242.4092	$1,242.42	$1,242.40	$1,242.30