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	$174.31	10.499%	$192.6108	$192.61	$192.60	$192.60
Purchase #2	$16.28	6.105%	$17.2739	$17.27	$17.25	$17.30
Purchase #3	$55.87	6.331%	$59.4071	$59.41	$59.40	$59.40
Purchase #4	$32.29	3.795%	$33.5154	$33.52	$33.50	$33.50
Purchase #5	$181.30	10.176%	$199.7491	$199.75	$199.75	$199.70
Purchase #6	$98.55	5.369%	$103.8411	$103.84	$103.85	$103.80
Purchase #7	$31.71	12.324%	$35.6179	$35.62	$35.60	$35.60
7 purchase totals =	$590.31		$642.0153	$642.02	$641.95	$641.90