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	$143.33	9.465%	$156.8962	$156.90	$156.90	$156.90
Purchase #2	$77.29	12.420%	$86.8894	$86.89	$86.90	$86.90
Purchase #3	$41.58	4.507%	$43.454	$43.45	$43.45	$43.50
Purchase #4	$229.58	9.102%	$250.4764	$250.48	$250.50	$250.50
Purchase #5	$59.60	13.186%	$67.4589	$67.46	$67.45	$67.50
Purchase #6	$85.56	4.627%	$89.5189	$89.52	$89.50	$89.50
Purchase #7	$187.42	8.835%	$203.9786	$203.98	$204.00	$204.00
7 purchase totals =	$824.36		$898.6724	$898.68	$898.70	$898.80