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	$189.88	3.519%	$196.5619	$196.56	$196.55	$196.60
Purchase #2	$92.97	10.858%	$103.0647	$103.06	$103.05	$103.10
Purchase #3	$142.32	7.428%	$152.8915	$152.89	$152.90	$152.90
Purchase #4	$134.51	8.731%	$146.2541	$146.25	$146.25	$146.30
Purchase #5	$87.53	6.307%	$93.0505	$93.05	$93.05	$93.10
Purchase #6	$78.59	10.583%	$86.9072	$86.91	$86.90	$86.90
Purchase #7	$60.36	4.420%	$63.0279	$63.03	$63.05	$63.00
7 purchase totals =	$786.16		$841.7578	$841.75	$841.75	$841.90