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	$28.25	3.673%	$29.2876	$29.29	$29.30	$29.30
Purchase #2	$19.88	4.373%	$20.7494	$20.75	$20.75	$20.70
Purchase #3	$33.56	5.852%	$35.5239	$35.52	$35.50	$35.50
Purchase #4	$180.85	9.822%	$198.6131	$198.61	$198.60	$198.60
Purchase #5	$9.75	11.125%	$10.8347	$10.83	$10.85	$10.80
Purchase #6	$229.59	3.193%	$236.9208	$236.92	$236.90	$236.90
Purchase #7	$130.90	8.843%	$142.4755	$142.48	$142.50	$142.50
7 purchase totals =	$632.78		$674.4050	$674.40	$674.40	$674.30