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	$133.27	9.453%	$145.868	$145.87	$145.85	$145.90
Purchase #2	$57.38	5.499%	$60.5353	$60.54	$60.55	$60.50
Purchase #3	$241.61	7.258%	$259.1461	$259.15	$259.15	$259.10
Purchase #4	$25.55	10.719%	$28.2887	$28.29	$28.30	$28.30
Purchase #5	$178.66	8.814%	$194.4071	$194.41	$194.40	$194.40
Purchase #6	$192.96	12.113%	$216.3332	$216.33	$216.35	$216.30
Purchase #7	$229.72	13.135%	$259.8937	$259.89	$259.90	$259.90
7 purchase totals =	$1,059.15		$1,164.4721	$1,164.48	$1,164.50	$1,164.40