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	$174.72	12.265%	$196.1494	$196.15	$196.15	$196.10
Purchase #2	$219.73	13.286%	$248.9233	$248.92	$248.90	$248.90
Purchase #3	$181.55	4.558%	$189.825	$189.83	$189.85	$189.80
Purchase #4	$57.38	8.810%	$62.4352	$62.44	$62.45	$62.40
Purchase #5	$38.73	10.200%	$42.6805	$42.68	$42.70	$42.70
Purchase #6	$241.30	8.363%	$261.4799	$261.48	$261.50	$261.50
Purchase #7	$53.33	5.706%	$56.373	$56.37	$56.35	$56.40
7 purchase totals =	$966.74		$1,057.8663	$1,057.87	$1,057.90	$1,057.80