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	$134.51	7.231%	$144.2364	$144.24	$144.25	$144.20
Purchase #2	$59.75	13.374%	$67.741	$67.74	$67.75	$67.70
Purchase #3	$202.36	12.361%	$227.3737	$227.37	$227.35	$227.40
Purchase #4	$146.26	8.382%	$158.5195	$158.52	$158.50	$158.50
Purchase #5	$96.79	5.852%	$102.4542	$102.45	$102.45	$102.50
Purchase #6	$214.90	11.115%	$238.7861	$238.79	$238.80	$238.80
Purchase #7	$146.48	12.814%	$165.2499	$165.25	$165.25	$165.20
7 purchase totals =	$1,001.05		$1,104.3608	$1,104.36	$1,104.35	$1,104.30