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	$33.41	5.869%	$35.3708	$35.37	$35.35	$35.40
Purchase #2	$183.37	8.104%	$198.2303	$198.23	$198.25	$198.20
Purchase #3	$170.97	5.738%	$180.7803	$180.78	$180.80	$180.80
Purchase #4	$50.33	4.405%	$52.547	$52.55	$52.55	$52.50
Purchase #5	$141.44	6.360%	$150.4356	$150.44	$150.45	$150.40
Purchase #6	$96.73	13.317%	$109.6115	$109.61	$109.60	$109.60
Purchase #7	$24.73	11.289%	$27.5218	$27.52	$27.50	$27.50
7 purchase totals =	$700.98		$754.4973	$754.50	$754.50	$754.40