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	$77.89	12.198%	$87.391	$87.39	$87.40	$87.40
Purchase #2	$110.75	6.330%	$117.7605	$117.76	$117.75	$117.80
Purchase #3	$142.95	10.757%	$158.3271	$158.33	$158.35	$158.30
Purchase #4	$162.61	5.711%	$171.8967	$171.90	$171.90	$171.90
Purchase #5	$231.73	4.305%	$241.706	$241.71	$241.70	$241.70
Purchase #6	$248.39	13.380%	$281.6246	$281.62	$281.60	$281.60
Purchase #7	$95.59	4.541%	$99.9307	$99.93	$99.95	$99.90
7 purchase totals =	$1,069.91		$1,158.6366	$1,158.64	$1,158.65	$1,158.60