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	$103.55	8.545%	$112.3983	$112.40	$112.40	$112.40
Purchase #2	$9.32	9.801%	$10.2335	$10.23	$10.25	$10.20
Purchase #3	$159.93	12.141%	$179.3471	$179.35	$179.35	$179.30
Purchase #4	$46.95	7.597%	$50.5168	$50.52	$50.50	$50.50
Purchase #5	$35.37	6.355%	$37.6178	$37.62	$37.60	$37.60
Purchase #6	$124.56	13.536%	$141.4204	$141.42	$141.40	$141.40
Purchase #7	$227.70	10.190%	$250.9026	$250.90	$250.90	$250.90
7 purchase totals =	$707.38		$782.4365	$782.44	$782.40	$782.30