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	$103.64	8.812%	$112.7728	$112.77	$112.75	$112.80
Purchase #2	$63.86	11.437%	$71.1637	$71.16	$71.15	$71.20
Purchase #3	$188.63	3.654%	$195.5225	$195.52	$195.50	$195.50
Purchase #4	$144.99	8.752%	$157.6795	$157.68	$157.70	$157.70
Purchase #5	$179.52	9.471%	$196.5223	$196.52	$196.50	$196.50
Purchase #6	$12.26	4.825%	$12.8515	$12.85	$12.85	$12.90
Purchase #7	$53.57	3.525%	$55.4583	$55.46	$55.45	$55.50
7 purchase totals =	$746.47		$801.9706	$801.96	$801.90	$802.10