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	$188.63	5.808%	$199.5856	$199.59	$199.60	$199.60
Purchase #2	$85.42	5.801%	$90.3752	$90.38	$90.40	$90.40
Purchase #3	$203.93	3.756%	$211.5896	$211.59	$211.60	$211.60
Purchase #4	$147.28	5.329%	$155.1286	$155.13	$155.15	$155.10
Purchase #5	$39.99	6.359%	$42.533	$42.53	$42.55	$42.50
Purchase #6	$35.26	6.441%	$37.5311	$37.53	$37.55	$37.50
Purchase #7	$228.74	4.200%	$238.3471	$238.35	$238.35	$238.30
7 purchase totals =	$929.25		$975.0902	$975.10	$975.20	$975.00