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	$132.71	9.788%	$145.6997	$145.70	$145.70	$145.70
Purchase #2	$150.57	12.464%	$169.337	$169.34	$169.35	$169.30
Purchase #3	$100.54	6.272%	$106.8459	$106.85	$106.85	$106.80
Purchase #4	$26.59	3.238%	$27.451	$27.45	$27.45	$27.50
Purchase #5	$85.62	4.681%	$89.6279	$89.63	$89.65	$89.60
Purchase #6	$202.92	11.641%	$226.5419	$226.54	$226.55	$226.50
Purchase #7	$229.33	12.638%	$258.3127	$258.31	$258.30	$258.30
7 purchase totals =	$928.28		$1,023.8161	$1,023.82	$1,023.85	$1,023.70