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	$165.98	10.478%	$183.3714	$183.37	$183.35	$183.40
Purchase #2	$48.86	13.595%	$55.5025	$55.50	$55.50	$55.50
Purchase #3	$215.28	9.833%	$236.4485	$236.45	$236.45	$236.40
Purchase #4	$236.80	6.326%	$251.78	$251.78	$251.80	$251.80
Purchase #5	$66.33	9.232%	$72.4536	$72.45	$72.45	$72.50
Purchase #6	$196.35	10.174%	$216.3266	$216.33	$216.35	$216.30
Purchase #7	$43.94	5.410%	$46.3172	$46.32	$46.30	$46.30
7 purchase totals =	$973.54		$1,062.1998	$1,062.20	$1,062.20	$1,062.20