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	$197.40	7.783%	$212.7636	$212.76	$212.75	$212.80
Purchase #2	$96.66	7.671%	$104.0748	$104.07	$104.05	$104.10
Purchase #3	$227.37	4.704%	$238.0655	$238.07	$238.05	$238.10
Purchase #4	$127.60	12.596%	$143.6725	$143.67	$143.65	$143.70
Purchase #5	$219.95	12.570%	$247.5977	$247.60	$247.60	$247.60
Purchase #6	$73.66	6.872%	$78.7219	$78.72	$78.70	$78.70
Purchase #7	$102.79	8.740%	$111.7738	$111.77	$111.75	$111.80
7 purchase totals =	$1,045.43		$1,136.6698	$1,136.66	$1,136.55	$1,136.80