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	$30.77	10.222%	$33.9153	$33.92	$33.90	$33.90
Purchase #2	$74.75	4.696%	$78.2603	$78.26	$78.25	$78.30
Purchase #3	$130.74	9.293%	$142.8897	$142.89	$142.90	$142.90
Purchase #4	$201.28	10.299%	$222.0098	$222.01	$222.00	$222.00
Purchase #5	$221.42	10.392%	$244.43	$244.43	$244.45	$244.40
Purchase #6	$31.67	6.574%	$33.752	$33.75	$33.75	$33.80
Purchase #7	$244.31	10.432%	$269.7964	$269.80	$269.80	$269.80
7 purchase totals =	$934.94		$1,025.0535	$1,025.06	$1,025.05	$1,025.10