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	$135.46	8.111%	$146.4472	$146.45	$146.45	$146.40
Purchase #2	$240.33	13.210%	$272.0776	$272.08	$272.10	$272.10
Purchase #3	$99.40	5.122%	$104.4913	$104.49	$104.50	$104.50
Purchase #4	$121.94	8.695%	$132.5427	$132.54	$132.55	$132.50
Purchase #5	$246.55	10.857%	$273.3179	$273.32	$273.30	$273.30
Purchase #6	$72.73	5.141%	$76.469	$76.47	$76.45	$76.50
Purchase #7	$80.45	11.156%	$89.425	$89.43	$89.45	$89.40
7 purchase totals =	$996.86		$1,094.7707	$1,094.78	$1,094.80	$1,094.70