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	$115.35	3.110%	$118.9374	$118.94	$118.95	$118.90
Purchase #2	$55.74	13.302%	$63.1545	$63.15	$63.15	$63.20
Purchase #3	$236.59	8.597%	$256.9296	$256.93	$256.95	$256.90
Purchase #4	$86.56	12.318%	$97.2225	$97.22	$97.20	$97.20
Purchase #5	$91.35	9.316%	$99.8602	$99.86	$99.85	$99.90
Purchase #6	$85.45	12.253%	$95.9202	$95.92	$95.90	$95.90
Purchase #7	$72.57	7.334%	$77.8923	$77.89	$77.90	$77.90
7 purchase totals =	$743.61		$809.9167	$809.91	$809.90	$809.90