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	$85.25	5.254%	$89.729	$89.73	$89.75	$89.70
Purchase #2	$201.49	7.645%	$216.8939	$216.89	$216.90	$216.90
Purchase #3	$246.83	10.843%	$273.5938	$273.59	$273.60	$273.60
Purchase #4	$81.42	6.685%	$86.8629	$86.86	$86.85	$86.90
Purchase #5	$52.32	3.752%	$54.283	$54.28	$54.30	$54.30
Purchase #6	$121.85	10.127%	$134.1897	$134.19	$134.20	$134.20
Purchase #7	$137.75	6.710%	$146.993	$146.99	$147.00	$147.00
7 purchase totals =	$926.91		$1,002.5453	$1,002.53	$1,002.60	$1,002.60