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	$59.81	6.306%	$63.5816	$63.58	$63.60	$63.60
Purchase #2	$31.73	6.421%	$33.7674	$33.77	$33.75	$33.80
Purchase #3	$185.92	7.796%	$200.4143	$200.41	$200.40	$200.40
Purchase #4	$98.27	13.600%	$111.6347	$111.63	$111.65	$111.60
Purchase #5	$65.53	11.858%	$73.3005	$73.30	$73.30	$73.30
Purchase #6	$47.74	3.641%	$49.4782	$49.48	$49.50	$49.50
Purchase #7	$24.83	11.231%	$27.6187	$27.62	$27.60	$27.60
7 purchase totals =	$513.83		$559.7954	$559.79	$559.80	$559.80