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	$71.47	13.749%	$81.2964	$81.30	$81.30	$81.30
Purchase #2	$5.84	10.276%	$6.4401	$6.44	$6.45	$6.40
Purchase #3	$98.34	6.689%	$104.918	$104.92	$104.90	$104.90
Purchase #4	$241.34	13.420%	$273.7278	$273.73	$273.75	$273.70
Purchase #5	$62.84	3.591%	$65.0966	$65.10	$65.10	$65.10
Purchase #6	$50.53	5.386%	$53.2515	$53.25	$53.25	$53.30
Purchase #7	$98.39	13.319%	$111.4946	$111.49	$111.50	$111.50
7 purchase totals =	$628.75		$696.2250	$696.23	$696.25	$696.20