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	$132.45	10.174%	$145.9255	$145.93	$145.95	$145.90
Purchase #2	$75.50	10.323%	$83.2939	$83.29	$83.30	$83.30
Purchase #3	$101.51	10.582%	$112.2518	$112.25	$112.25	$112.30
Purchase #4	$19.83	7.434%	$21.3042	$21.30	$21.30	$21.30
Purchase #5	$104.34	8.253%	$112.9512	$112.95	$112.95	$113.00
Purchase #6	$191.52	6.666%	$204.2867	$204.29	$204.30	$204.30
Purchase #7	$72.83	10.435%	$80.4298	$80.43	$80.45	$80.40
7 purchase totals =	$697.98		$760.4431	$760.44	$760.50	$760.50