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	$46.32	8.159%	$50.0992	$50.10	$50.10	$50.10
Purchase #2	$12.30	13.222%	$13.9263	$13.93	$13.95	$13.90
Purchase #3	$73.35	12.328%	$82.3926	$82.39	$82.40	$82.40
Purchase #4	$171.63	11.531%	$191.4207	$191.42	$191.40	$191.40
Purchase #5	$150.48	9.190%	$164.3091	$164.31	$164.30	$164.30
Purchase #6	$101.72	4.215%	$106.0075	$106.01	$106.00	$106.00
Purchase #7	$16.95	10.755%	$18.773	$18.77	$18.75	$18.80
7 purchase totals =	$572.75		$626.9284	$626.93	$626.90	$626.90