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	$83.91	10.717%	$92.9026	$92.90	$92.90	$92.90
Purchase #2	$76.69	10.548%	$84.7793	$84.78	$84.80	$84.80
Purchase #3	$53.27	6.442%	$56.7017	$56.70	$56.70	$56.70
Purchase #4	$69.61	4.570%	$72.7912	$72.79	$72.80	$72.80
Purchase #5	$19.33	13.854%	$22.008	$22.01	$22.00	$22.00
Purchase #6	$54.58	9.200%	$59.6014	$59.60	$59.60	$59.60
Purchase #7	$82.27	7.504%	$88.4435	$88.44	$88.45	$88.40
7 purchase totals =	$439.66		$477.2277	$477.22	$477.25	$477.20