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	$82.71	3.413%	$85.5329	$85.53	$85.55	$85.50
Purchase #2	$138.62	8.439%	$150.3181	$150.32	$150.30	$150.30
Purchase #3	$30.28	6.184%	$32.1525	$32.15	$32.15	$32.20
Purchase #4	$179.75	7.839%	$193.8406	$193.84	$193.85	$193.80
Purchase #5	$88.92	8.568%	$96.5387	$96.54	$96.55	$96.50
Purchase #6	$181.86	9.602%	$199.3222	$199.32	$199.30	$199.30
Purchase #7	$229.90	9.434%	$251.5888	$251.59	$251.60	$251.60
7 purchase totals =	$932.04		$1,009.2938	$1,009.29	$1,009.30	$1,009.20