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	$97.63	5.479%	$102.9791	$102.98	$103.00	$103.00
Purchase #2	$136.53	10.432%	$150.7728	$150.77	$150.75	$150.80
Purchase #3	$190.63	7.191%	$204.3382	$204.34	$204.35	$204.30
Purchase #4	$185.60	13.335%	$210.3498	$210.35	$210.35	$210.30
Purchase #5	$229.54	10.367%	$253.3364	$253.34	$253.35	$253.30
Purchase #6	$34.83	5.314%	$36.6809	$36.68	$36.70	$36.70
Purchase #7	$53.98	7.239%	$57.8876	$57.89	$57.90	$57.90
7 purchase totals =	$928.74		$1,016.3448	$1,016.35	$1,016.40	$1,016.30