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	$209.34	4.531%	$218.8252	$218.83	$218.85	$218.80
Purchase #2	$168.30	13.391%	$190.8371	$190.84	$190.85	$190.80
Purchase #3	$233.72	4.178%	$243.4848	$243.48	$243.50	$243.50
Purchase #4	$145.34	7.787%	$156.6576	$156.66	$156.65	$156.70
Purchase #5	$89.44	11.870%	$100.0565	$100.06	$100.05	$100.10
Purchase #6	$220.26	6.846%	$235.339	$235.34	$235.35	$235.30
Purchase #7	$150.86	4.853%	$158.1812	$158.18	$158.20	$158.20
7 purchase totals =	$1,217.26		$1,303.3814	$1,303.39	$1,303.45	$1,303.40