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	$33.77	8.212%	$36.5432	$36.54	$36.55	$36.50
Purchase #2	$212.66	13.117%	$240.5546	$240.55	$240.55	$240.60
Purchase #3	$203.63	4.394%	$212.5775	$212.58	$212.60	$212.60
Purchase #4	$145.66	9.566%	$159.5938	$159.59	$159.60	$159.60
Purchase #5	$83.37	8.814%	$90.7182	$90.72	$90.70	$90.70
Purchase #6	$24.77	4.444%	$25.8708	$25.87	$25.85	$25.90
Purchase #7	$235.89	7.514%	$253.6148	$253.61	$253.60	$253.60
7 purchase totals =	$939.75		$1,019.4729	$1,019.46	$1,019.45	$1,019.50