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	$133.27	6.320%	$141.6927	$141.69	$141.70	$141.70
Purchase #2	$85.48	6.580%	$91.1046	$91.10	$91.10	$91.10
Purchase #3	$247.51	7.794%	$266.8009	$266.80	$266.80	$266.80
Purchase #4	$59.81	5.200%	$62.9201	$62.92	$62.90	$62.90
Purchase #5	$128.41	12.510%	$144.4741	$144.47	$144.45	$144.50
Purchase #6	$83.75	10.521%	$92.5613	$92.56	$92.55	$92.60
Purchase #7	$211.40	4.235%	$220.3528	$220.35	$220.35	$220.40
7 purchase totals =	$949.63		$1,019.9065	$1,019.89	$1,019.85	$1,020.00