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	$238.89	3.643%	$247.5928	$247.59	$247.60	$247.60
Purchase #2	$89.72	3.639%	$92.9849	$92.98	$93.00	$93.00
Purchase #3	$197.34	4.738%	$206.69	$206.69	$206.70	$206.70
Purchase #4	$97.76	11.634%	$109.1334	$109.13	$109.15	$109.10
Purchase #5	$150.81	9.287%	$164.8157	$164.82	$164.80	$164.80
Purchase #6	$119.46	11.162%	$132.7941	$132.79	$132.80	$132.80
Purchase #7	$126.88	12.169%	$142.32	$142.32	$142.30	$142.30
7 purchase totals =	$1,020.86		$1,096.3309	$1,096.32	$1,096.35	$1,096.30