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	$53.48	11.264%	$59.504	$59.50	$59.50	$59.50
Purchase #2	$242.84	11.161%	$269.9434	$269.94	$269.95	$269.90
Purchase #3	$161.51	10.458%	$178.4007	$178.40	$178.40	$178.40
Purchase #4	$82.29	11.865%	$92.0537	$92.05	$92.05	$92.10
Purchase #5	$220.27	5.219%	$231.7659	$231.77	$231.75	$231.80
Purchase #6	$91.30	8.846%	$99.3764	$99.38	$99.40	$99.40
Purchase #7	$215.41	12.646%	$242.6507	$242.65	$242.65	$242.70
7 purchase totals =	$1,067.10		$1,173.6948	$1,173.69	$1,173.70	$1,173.80