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	$134.85	6.734%	$143.9308	$143.93	$143.95	$143.90
Purchase #2	$214.43	8.860%	$233.4285	$233.43	$233.45	$233.40
Purchase #3	$99.73	7.179%	$106.8896	$106.89	$106.90	$106.90
Purchase #4	$68.65	7.510%	$73.8056	$73.81	$73.80	$73.80
Purchase #5	$57.34	7.740%	$61.7781	$61.78	$61.80	$61.80
Purchase #6	$85.31	4.371%	$89.0389	$89.04	$89.05	$89.00
Purchase #7	$72.30	3.129%	$74.5623	$74.56	$74.55	$74.60
7 purchase totals =	$732.61		$783.4338	$783.44	$783.50	$783.40