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	$99.99	3.573%	$103.5626	$103.56	$103.55	$103.60
Purchase #2	$10.32	5.504%	$10.888	$10.89	$10.90	$10.90
Purchase #3	$100.94	4.638%	$105.6216	$105.62	$105.60	$105.60
Purchase #4	$5.81	11.548%	$6.4809	$6.48	$6.50	$6.50
Purchase #5	$243.87	12.174%	$273.5587	$273.56	$273.55	$273.60
Purchase #6	$137.58	12.104%	$154.2327	$154.23	$154.25	$154.20
Purchase #7	$190.32	4.784%	$199.4249	$199.42	$199.40	$199.40
7 purchase totals =	$788.83		$853.7694	$853.76	$853.75	$853.80