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	$214.99	3.666%	$222.8715	$222.87	$222.85	$222.90
Purchase #2	$24.82	10.155%	$27.3405	$27.34	$27.35	$27.30
Purchase #3	$147.73	6.835%	$157.8273	$157.83	$157.85	$157.80
Purchase #4	$51.93	6.689%	$55.4036	$55.40	$55.40	$55.40
Purchase #5	$18.89	10.334%	$20.8421	$20.84	$20.85	$20.80
Purchase #6	$95.65	11.378%	$106.5331	$106.53	$106.55	$106.50
Purchase #7	$54.54	6.180%	$57.9106	$57.91	$57.90	$57.90
7 purchase totals =	$608.55		$648.7287	$648.72	$648.75	$648.60