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	$60.33	11.633%	$67.3482	$67.35	$67.35	$67.30
Purchase #2	$98.98	3.615%	$102.5581	$102.56	$102.55	$102.60
Purchase #3	$215.34	8.246%	$233.0969	$233.10	$233.10	$233.10
Purchase #4	$88.46	12.523%	$99.5378	$99.54	$99.55	$99.50
Purchase #5	$26.37	7.600%	$28.3741	$28.37	$28.35	$28.40
Purchase #6	$82.81	5.673%	$87.5078	$87.51	$87.50	$87.50
Purchase #7	$175.60	3.251%	$181.3088	$181.31	$181.30	$181.30
7 purchase totals =	$747.89		$799.7317	$799.74	$799.70	$799.70