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	$139.93	12.148%	$156.9287	$156.93	$156.95	$156.90
Purchase #2	$105.73	5.662%	$111.7164	$111.72	$111.70	$111.70
Purchase #3	$6.71	12.426%	$7.5438	$7.54	$7.55	$7.50
Purchase #4	$212.26	6.183%	$225.384	$225.38	$225.40	$225.40
Purchase #5	$148.60	12.452%	$167.1037	$167.10	$167.10	$167.10
Purchase #6	$196.91	13.745%	$223.9753	$223.98	$224.00	$224.00
Purchase #7	$91.52	3.365%	$94.5996	$94.60	$94.60	$94.60
7 purchase totals =	$901.66		$987.2515	$987.25	$987.30	$987.20