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	$137.29	13.795%	$156.2292	$156.23	$156.25	$156.20
Purchase #2	$164.85	6.437%	$175.4614	$175.46	$175.45	$175.50
Purchase #3	$220.29	11.470%	$245.5573	$245.56	$245.55	$245.60
Purchase #4	$118.31	11.442%	$131.847	$131.85	$131.85	$131.80
Purchase #5	$61.81	6.474%	$65.8116	$65.81	$65.80	$65.80
Purchase #6	$75.76	5.423%	$79.8685	$79.87	$79.85	$79.90
Purchase #7	$35.42	7.316%	$38.0113	$38.01	$38.00	$38.00
7 purchase totals =	$813.73		$892.7863	$892.79	$892.75	$892.80