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	$29.84	9.814%	$32.7685	$32.77	$32.75	$32.80
Purchase #2	$42.97	13.521%	$48.78	$48.78	$48.80	$48.80
Purchase #3	$234.32	13.456%	$265.8501	$265.85	$265.85	$265.90
Purchase #4	$52.86	12.839%	$59.6467	$59.65	$59.65	$59.60
Purchase #5	$65.62	12.711%	$73.961	$73.96	$73.95	$74.00
Purchase #6	$63.49	13.865%	$72.2929	$72.29	$72.30	$72.30
Purchase #7	$247.53	9.441%	$270.8993	$270.90	$270.90	$270.90
7 purchase totals =	$736.63		$824.1985	$824.20	$824.20	$824.30