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	$216.72	3.790%	$224.9337	$224.93	$224.95	$224.90
Purchase #2	$94.63	6.321%	$100.6116	$100.61	$100.60	$100.60
Purchase #3	$126.90	12.564%	$142.8437	$142.84	$142.85	$142.80
Purchase #4	$205.30	6.581%	$218.8108	$218.81	$218.80	$218.80
Purchase #5	$37.98	4.114%	$39.5425	$39.54	$39.55	$39.50
Purchase #6	$204.72	9.108%	$223.3659	$223.37	$223.35	$223.40
Purchase #7	$77.60	7.360%	$83.3114	$83.31	$83.30	$83.30
7 purchase totals =	$963.85		$1,033.4196	$1,033.41	$1,033.40	$1,033.30