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	$248.85	13.681%	$282.8952	$282.90	$282.90	$282.90
Purchase #2	$89.26	4.645%	$93.4061	$93.41	$93.40	$93.40
Purchase #3	$53.63	11.635%	$59.8699	$59.87	$59.85	$59.90
Purchase #4	$75.46	13.339%	$85.5256	$85.53	$85.55	$85.50
Purchase #5	$80.36	9.134%	$87.7001	$87.70	$87.70	$87.70
Purchase #6	$206.56	13.572%	$234.5943	$234.59	$234.60	$234.60
Purchase #7	$218.38	6.768%	$233.16	$233.16	$233.15	$233.20
7 purchase totals =	$972.50		$1,077.1512	$1,077.16	$1,077.15	$1,077.20