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	$129.58	12.116%	$145.2799	$145.28	$145.30	$145.30
Purchase #2	$120.32	6.646%	$128.3165	$128.32	$128.30	$128.30
Purchase #3	$114.40	8.500%	$124.124	$124.12	$124.10	$124.10
Purchase #4	$37.87	13.374%	$42.9347	$42.93	$42.95	$42.90
Purchase #5	$83.94	5.164%	$88.2747	$88.27	$88.25	$88.30
Purchase #6	$168.95	9.586%	$185.1455	$185.15	$185.15	$185.10
Purchase #7	$49.72	4.473%	$51.944	$51.94	$51.95	$51.90
7 purchase totals =	$704.78		$766.0193	$766.01	$766.00	$765.90