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	$56.80	10.608%	$62.8253	$62.83	$62.85	$62.80
Purchase #2	$196.94	12.789%	$222.1267	$222.13	$222.15	$222.10
Purchase #3	$60.64	10.747%	$67.157	$67.16	$67.15	$67.20
Purchase #4	$79.99	10.564%	$88.4401	$88.44	$88.45	$88.40
Purchase #5	$243.83	7.676%	$262.5464	$262.55	$262.55	$262.50
Purchase #6	$30.98	8.132%	$33.4993	$33.50	$33.50	$33.50
Purchase #7	$68.94	13.349%	$78.1428	$78.14	$78.15	$78.10
7 purchase totals =	$738.12		$814.7376	$814.75	$814.80	$814.60