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	$144.61	5.776%	$152.9627	$152.96	$152.95	$153.00
Purchase #2	$86.25	7.289%	$92.5368	$92.54	$92.55	$92.50
Purchase #3	$166.71	11.135%	$185.2732	$185.27	$185.25	$185.30
Purchase #4	$138.76	9.120%	$151.4149	$151.41	$151.40	$151.40
Purchase #5	$135.95	5.458%	$143.3702	$143.37	$143.35	$143.40
Purchase #6	$16.79	10.827%	$18.6079	$18.61	$18.60	$18.60
Purchase #7	$123.93	3.460%	$128.218	$128.22	$128.20	$128.20
7 purchase totals =	$813.00		$872.3837	$872.38	$872.30	$872.40