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	$82.72	10.334%	$91.2683	$91.27	$91.25	$91.30
Purchase #2	$218.28	11.166%	$242.6531	$242.65	$242.65	$242.70
Purchase #3	$83.61	4.691%	$87.5321	$87.53	$87.55	$87.50
Purchase #4	$60.61	10.637%	$67.0571	$67.06	$67.05	$67.10
Purchase #5	$66.84	7.504%	$71.8557	$71.86	$71.85	$71.90
Purchase #6	$57.56	4.179%	$59.9654	$59.97	$59.95	$60.00
Purchase #7	$68.44	6.224%	$72.6997	$72.70	$72.70	$72.70
7 purchase totals =	$638.06		$693.0314	$693.04	$693.00	$693.20