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	$173.67	10.274%	$191.5129	$191.51	$191.50	$191.50
Purchase #2	$62.42	5.812%	$66.0479	$66.05	$66.05	$66.00
Purchase #3	$125.32	6.448%	$133.4006	$133.40	$133.40	$133.40
Purchase #4	$80.32	7.685%	$86.4926	$86.49	$86.50	$86.50
Purchase #5	$240.33	3.384%	$248.4628	$248.46	$248.45	$248.50
Purchase #6	$57.46	4.239%	$59.8957	$59.90	$59.90	$59.90
Purchase #7	$59.45	10.199%	$65.5133	$65.51	$65.50	$65.50
7 purchase totals =	$798.97		$851.3258	$851.32	$851.30	$851.30