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	$61.38	13.687%	$69.7811	$69.78	$69.80	$69.80
Purchase #2	$243.56	7.273%	$261.2741	$261.27	$261.25	$261.30
Purchase #3	$58.55	7.383%	$62.8727	$62.87	$62.85	$62.90
Purchase #4	$150.74	4.356%	$157.3062	$157.31	$157.30	$157.30
Purchase #5	$56.60	5.607%	$59.7736	$59.77	$59.75	$59.80
Purchase #6	$152.67	10.411%	$168.5645	$168.56	$168.55	$168.60
Purchase #7	$112.85	7.220%	$120.9978	$121.00	$121.00	$121.00
7 purchase totals =	$836.35		$900.5700	$900.56	$900.50	$900.70