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	$143.91	11.133%	$159.9315	$159.93	$159.95	$159.90
Purchase #2	$178.70	12.292%	$200.6658	$200.67	$200.65	$200.70
Purchase #3	$52.48	7.483%	$56.4071	$56.41	$56.40	$56.40
Purchase #4	$39.26	9.219%	$42.8794	$42.88	$42.90	$42.90
Purchase #5	$119.58	6.530%	$127.3886	$127.39	$127.40	$127.40
Purchase #6	$117.68	3.114%	$121.3446	$121.34	$121.35	$121.30
Purchase #7	$78.85	12.836%	$88.9712	$88.97	$88.95	$89.00
7 purchase totals =	$730.46		$797.5882	$797.59	$797.60	$797.60