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	$43.55	11.353%	$48.4942	$48.49	$48.50	$48.50
Purchase #2	$81.47	8.224%	$88.1701	$88.17	$88.15	$88.20
Purchase #3	$88.31	13.581%	$100.3034	$100.30	$100.30	$100.30
Purchase #4	$218.37	4.779%	$228.8059	$228.81	$228.80	$228.80
Purchase #5	$138.80	11.511%	$154.7773	$154.78	$154.80	$154.80
Purchase #6	$188.90	4.110%	$196.6638	$196.66	$196.65	$196.70
Purchase #7	$106.58	7.443%	$114.5127	$114.51	$114.50	$114.50
7 purchase totals =	$865.98		$931.7274	$931.72	$931.70	$931.80