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	$73.95	9.206%	$80.7578	$80.76	$80.75	$80.80
Purchase #2	$19.87	13.795%	$22.6111	$22.61	$22.60	$22.60
Purchase #3	$140.53	5.695%	$148.5332	$148.53	$148.55	$148.50
Purchase #4	$88.96	10.304%	$98.1264	$98.13	$98.15	$98.10
Purchase #5	$216.33	7.834%	$233.2773	$233.28	$233.30	$233.30
Purchase #6	$173.33	3.812%	$179.9373	$179.94	$179.95	$179.90
Purchase #7	$160.41	7.792%	$172.9091	$172.91	$172.90	$172.90
7 purchase totals =	$873.38		$936.1522	$936.16	$936.20	$936.10