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	$141.99	7.697%	$152.919	$152.92	$152.90	$152.90
Purchase #2	$102.90	4.721%	$107.7579	$107.76	$107.75	$107.80
Purchase #3	$232.81	6.490%	$247.9194	$247.92	$247.90	$247.90
Purchase #4	$38.71	9.711%	$42.4691	$42.47	$42.45	$42.50
Purchase #5	$77.91	6.693%	$83.1245	$83.12	$83.10	$83.10
Purchase #6	$24.44	11.745%	$27.3105	$27.31	$27.30	$27.30
Purchase #7	$178.46	4.117%	$185.8072	$185.81	$185.80	$185.80
7 purchase totals =	$797.22		$847.3076	$847.31	$847.20	$847.30