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	$77.42	6.383%	$82.3617	$82.36	$82.35	$82.40
Purchase #2	$66.77	4.476%	$69.7586	$69.76	$69.75	$69.80
Purchase #3	$54.95	4.758%	$57.5645	$57.56	$57.55	$57.60
Purchase #4	$40.25	13.868%	$45.8319	$45.83	$45.85	$45.80
Purchase #5	$114.32	3.408%	$118.216	$118.22	$118.20	$118.20
Purchase #6	$248.35	7.847%	$267.838	$267.84	$267.85	$267.80
Purchase #7	$48.26	8.414%	$52.3206	$52.32	$52.30	$52.30
7 purchase totals =	$650.32		$693.8913	$693.89	$693.85	$693.90