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	$82.31	8.663%	$89.4405	$89.44	$89.45	$89.40
Purchase #2	$175.54	6.465%	$186.8887	$186.89	$186.90	$186.90
Purchase #3	$163.34	11.187%	$181.6128	$181.61	$181.60	$181.60
Purchase #4	$241.53	9.430%	$264.3063	$264.31	$264.30	$264.30
Purchase #5	$238.55	9.645%	$261.5581	$261.56	$261.55	$261.60
Purchase #6	$206.39	8.145%	$223.2005	$223.20	$223.20	$223.20
Purchase #7	$25.61	5.759%	$27.0849	$27.08	$27.10	$27.10
7 purchase totals =	$1,133.27		$1,234.0918	$1,234.09	$1,234.10	$1,234.10