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	$110.89	7.616%	$119.3354	$119.34	$119.35	$119.30
Purchase #2	$31.26	3.794%	$32.446	$32.45	$32.45	$32.40
Purchase #3	$112.63	13.484%	$127.817	$127.82	$127.80	$127.80
Purchase #4	$93.81	9.199%	$102.4396	$102.44	$102.45	$102.40
Purchase #5	$124.54	10.573%	$137.7076	$137.71	$137.70	$137.70
Purchase #6	$125.38	8.756%	$136.3583	$136.36	$136.35	$136.40
Purchase #7	$70.53	9.838%	$77.4687	$77.47	$77.45	$77.50
7 purchase totals =	$669.04		$733.5726	$733.59	$733.55	$733.50