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	$153.69	7.190%	$164.7403	$164.74	$164.75	$164.70
Purchase #2	$227.48	10.509%	$251.3859	$251.39	$251.40	$251.40
Purchase #3	$204.91	5.380%	$215.9342	$215.93	$215.95	$215.90
Purchase #4	$82.44	13.205%	$93.3262	$93.33	$93.35	$93.30
Purchase #5	$40.26	4.722%	$42.1611	$42.16	$42.15	$42.20
Purchase #6	$20.83	4.856%	$21.8415	$21.84	$21.85	$21.80
Purchase #7	$30.69	10.569%	$33.9336	$33.93	$33.95	$33.90
7 purchase totals =	$760.30		$823.3228	$823.32	$823.40	$823.20