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	$183.78	8.403%	$199.223	$199.22	$199.20	$199.20
Purchase #2	$37.30	10.336%	$41.1553	$41.16	$41.15	$41.20
Purchase #3	$222.54	9.801%	$244.3511	$244.35	$244.35	$244.40
Purchase #4	$80.33	12.552%	$90.413	$90.41	$90.40	$90.40
Purchase #5	$241.90	8.128%	$261.5616	$261.56	$261.55	$261.60
Purchase #6	$78.45	4.775%	$82.196	$82.20	$82.20	$82.20
Purchase #7	$85.28	6.516%	$90.8368	$90.84	$90.85	$90.80
7 purchase totals =	$929.58		$1,009.7368	$1,009.74	$1,009.70	$1,009.80