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	$154.78	4.836%	$162.2652	$162.27	$162.25	$162.30
Purchase #2	$53.47	4.820%	$56.0473	$56.05	$56.05	$56.00
Purchase #3	$66.41	7.799%	$71.5893	$71.59	$71.60	$71.60
Purchase #4	$180.56	10.278%	$199.118	$199.12	$199.10	$199.10
Purchase #5	$84.54	7.751%	$91.0927	$91.09	$91.10	$91.10
Purchase #6	$131.26	4.622%	$137.3268	$137.33	$137.35	$137.30
Purchase #7	$225.33	3.554%	$233.3382	$233.34	$233.35	$233.30
7 purchase totals =	$896.35		$950.7775	$950.79	$950.80	$950.70