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	$174.86	9.139%	$190.8405	$190.84	$190.85	$190.80
Purchase #2	$187.87	7.302%	$201.5883	$201.59	$201.60	$201.60
Purchase #3	$9.50	8.383%	$10.2964	$10.30	$10.30	$10.30
Purchase #4	$122.35	7.521%	$131.5519	$131.55	$131.55	$131.60
Purchase #5	$86.40	4.301%	$90.1161	$90.12	$90.10	$90.10
Purchase #6	$120.86	5.683%	$127.7285	$127.73	$127.75	$127.70
Purchase #7	$41.33	11.513%	$46.0883	$46.09	$46.10	$46.10
7 purchase totals =	$743.17		$798.2100	$798.22	$798.25	$798.20