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	$185.87	5.557%	$196.1988	$196.20	$196.20	$196.20
Purchase #2	$228.61	6.653%	$243.8194	$243.82	$243.80	$243.80
Purchase #3	$208.50	4.442%	$217.7616	$217.76	$217.75	$217.80
Purchase #4	$72.56	13.661%	$82.4724	$82.47	$82.45	$82.50
Purchase #5	$48.33	13.167%	$54.6936	$54.69	$54.70	$54.70
Purchase #6	$47.73	4.339%	$49.801	$49.80	$49.80	$49.80
Purchase #7	$196.97	5.605%	$208.0102	$208.01	$208.00	$208.00
7 purchase totals =	$988.57		$1,052.7570	$1,052.75	$1,052.70	$1,052.80