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	$164.79	4.654%	$172.4593	$172.46	$172.45	$172.50
Purchase #2	$19.47	9.174%	$21.2562	$21.26	$21.25	$21.30
Purchase #3	$171.27	11.185%	$190.4265	$190.43	$190.45	$190.40
Purchase #4	$120.57	11.489%	$134.4223	$134.42	$134.40	$134.40
Purchase #5	$195.69	4.348%	$204.1986	$204.20	$204.20	$204.20
Purchase #6	$153.49	9.817%	$168.5581	$168.56	$168.55	$168.60
Purchase #7	$88.25	8.591%	$95.8316	$95.83	$95.85	$95.80
7 purchase totals =	$913.53		$987.1526	$987.16	$987.15	$987.20