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	$109.89	8.834%	$119.5977	$119.60	$119.60	$119.60
Purchase #2	$199.54	10.152%	$219.7973	$219.80	$219.80	$219.80
Purchase #3	$12.89	7.739%	$13.8876	$13.89	$13.90	$13.90
Purchase #4	$249.96	3.287%	$258.1762	$258.18	$258.20	$258.20
Purchase #5	$211.96	5.751%	$224.1498	$224.15	$224.15	$224.10
Purchase #6	$180.61	8.269%	$195.5446	$195.54	$195.55	$195.50
Purchase #7	$211.31	10.447%	$233.3856	$233.39	$233.40	$233.40
7 purchase totals =	$1,176.16		$1,264.5388	$1,264.55	$1,264.60	$1,264.50