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	$244.33	7.542%	$262.7574	$262.76	$262.75	$262.80
Purchase #2	$188.25	11.694%	$210.264	$210.26	$210.25	$210.30
Purchase #3	$140.36	11.266%	$156.173	$156.17	$156.15	$156.20
Purchase #4	$19.58	8.830%	$21.3089	$21.31	$21.30	$21.30
Purchase #5	$118.51	4.467%	$123.8038	$123.80	$123.80	$123.80
Purchase #6	$171.25	10.119%	$188.5788	$188.58	$188.60	$188.60
Purchase #7	$225.72	3.436%	$233.4757	$233.48	$233.50	$233.50
7 purchase totals =	$1,108.00		$1,196.3616	$1,196.36	$1,196.35	$1,196.50