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	$80.41	12.572%	$90.5191	$90.52	$90.50	$90.50
Purchase #2	$43.34	9.492%	$47.4538	$47.45	$47.45	$47.50
Purchase #3	$5.37	12.404%	$6.0361	$6.04	$6.05	$6.00
Purchase #4	$166.76	9.669%	$182.884	$182.88	$182.90	$182.90
Purchase #5	$166.69	10.534%	$184.2491	$184.25	$184.25	$184.20
Purchase #6	$238.53	8.256%	$258.223	$258.22	$258.20	$258.20
Purchase #7	$238.39	3.687%	$247.1794	$247.18	$247.20	$247.20
7 purchase totals =	$939.49		$1,016.5445	$1,016.54	$1,016.55	$1,016.50