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	$10.43	12.869%	$11.7722	$11.77	$11.75	$11.80
Purchase #2	$137.59	11.711%	$153.7032	$153.70	$153.70	$153.70
Purchase #3	$87.56	4.443%	$91.4503	$91.45	$91.45	$91.50
Purchase #4	$79.89	4.815%	$83.7367	$83.74	$83.75	$83.70
Purchase #5	$139.42	9.769%	$153.0399	$153.04	$153.05	$153.00
Purchase #6	$123.55	3.820%	$128.2696	$128.27	$128.25	$128.30
Purchase #7	$80.74	6.147%	$85.7031	$85.70	$85.70	$85.70
7 purchase totals =	$659.18		$707.6750	$707.67	$707.65	$707.70