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	$33.40	7.352%	$35.8556	$35.86	$35.85	$35.90
Purchase #2	$142.94	13.556%	$162.3169	$162.32	$162.30	$162.30
Purchase #3	$24.82	10.607%	$27.4527	$27.45	$27.45	$27.50
Purchase #4	$83.61	10.545%	$92.4267	$92.43	$92.45	$92.40
Purchase #5	$99.33	10.681%	$109.9394	$109.94	$109.95	$109.90
Purchase #6	$198.81	12.301%	$223.2656	$223.27	$223.25	$223.30
Purchase #7	$47.33	6.670%	$50.4869	$50.49	$50.50	$50.50
7 purchase totals =	$630.24		$701.7438	$701.76	$701.75	$701.80