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	$73.82	4.216%	$76.9323	$76.93	$76.95	$76.90
Purchase #2	$103.61	7.845%	$111.7382	$111.74	$111.75	$111.70
Purchase #3	$69.61	6.699%	$74.2732	$74.27	$74.25	$74.30
Purchase #4	$165.46	12.771%	$186.5909	$186.59	$186.60	$186.60
Purchase #5	$238.56	11.380%	$265.7081	$265.71	$265.70	$265.70
Purchase #6	$90.28	4.107%	$93.9878	$93.99	$94.00	$94.00
Purchase #7	$81.53	9.694%	$89.4335	$89.43	$89.45	$89.40
7 purchase totals =	$822.87		$898.6640	$898.66	$898.70	$898.60