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	$188.40	4.201%	$196.3147	$196.31	$196.30	$196.30
Purchase #2	$188.40	6.488%	$200.6234	$200.62	$200.60	$200.60
Purchase #3	$182.35	12.256%	$204.6988	$204.70	$204.70	$204.70
Purchase #4	$102.67	11.661%	$114.6423	$114.64	$114.65	$114.60
Purchase #5	$82.77	4.763%	$86.7123	$86.71	$86.70	$86.70
Purchase #6	$144.30	6.692%	$153.9566	$153.96	$153.95	$154.00
Purchase #7	$90.68	3.458%	$93.8157	$93.82	$93.80	$93.80
7 purchase totals =	$979.57		$1,050.7638	$1,050.76	$1,050.70	$1,050.70