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	$114.66	8.646%	$124.5735	$124.57	$124.55	$124.60
Purchase #2	$102.82	8.246%	$111.2985	$111.30	$111.30	$111.30
Purchase #3	$67.96	4.815%	$71.2323	$71.23	$71.25	$71.20
Purchase #4	$127.94	13.705%	$145.4742	$145.47	$145.45	$145.50
Purchase #5	$39.64	9.577%	$43.4363	$43.44	$43.45	$43.40
Purchase #6	$191.37	5.636%	$202.1556	$202.16	$202.15	$202.20
Purchase #7	$197.34	13.150%	$223.2902	$223.29	$223.30	$223.30
7 purchase totals =	$841.73		$921.4606	$921.46	$921.45	$921.50