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	$97.61	6.844%	$104.2904	$104.29	$104.30	$104.30
Purchase #2	$187.28	5.160%	$196.9436	$196.94	$196.95	$196.90
Purchase #3	$17.85	5.254%	$18.7878	$18.79	$18.80	$18.80
Purchase #4	$42.57	9.819%	$46.7499	$46.75	$46.75	$46.70
Purchase #5	$140.77	7.583%	$151.4446	$151.44	$151.45	$151.40
Purchase #6	$249.41	8.450%	$270.4851	$270.49	$270.50	$270.50
Purchase #7	$41.37	3.335%	$42.7497	$42.75	$42.75	$42.70
7 purchase totals =	$776.86		$831.4511	$831.45	$831.50	$831.30