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	$205.69	4.655%	$215.2649	$215.26	$215.25	$215.30
Purchase #2	$115.73	7.216%	$124.0811	$124.08	$124.10	$124.10
Purchase #3	$127.89	7.504%	$137.4869	$137.49	$137.50	$137.50
Purchase #4	$74.81	10.127%	$82.386	$82.39	$82.40	$82.40
Purchase #5	$30.45	6.485%	$32.4247	$32.42	$32.40	$32.40
Purchase #6	$82.89	7.653%	$89.2336	$89.23	$89.25	$89.20
Purchase #7	$69.83	11.568%	$77.9079	$77.91	$77.90	$77.90
7 purchase totals =	$707.29		$758.7851	$758.78	$758.80	$758.80