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	$195.95	12.314%	$220.0793	$220.08	$220.10	$220.10
Purchase #2	$11.52	7.696%	$12.4066	$12.41	$12.40	$12.40
Purchase #3	$151.83	4.253%	$158.2873	$158.29	$158.30	$158.30
Purchase #4	$82.49	8.362%	$89.3878	$89.39	$89.40	$89.40
Purchase #5	$114.73	4.359%	$119.7311	$119.73	$119.75	$119.70
Purchase #6	$57.82	6.168%	$61.3863	$61.39	$61.40	$61.40
Purchase #7	$191.72	12.622%	$215.9189	$215.92	$215.90	$215.90
7 purchase totals =	$806.06		$877.1973	$877.21	$877.25	$877.20