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	$166.69	11.151%	$185.2776	$185.28	$185.30	$185.30
Purchase #2	$63.44	13.345%	$71.9061	$71.91	$71.90	$71.90
Purchase #3	$179.67	3.425%	$185.8237	$185.82	$185.80	$185.80
Purchase #4	$179.47	4.161%	$186.9377	$186.94	$186.95	$186.90
Purchase #5	$162.50	5.280%	$171.08	$171.08	$171.10	$171.10
Purchase #6	$190.94	5.732%	$201.8847	$201.88	$201.90	$201.90
Purchase #7	$176.70	11.686%	$197.3492	$197.35	$197.35	$197.30
7 purchase totals =	$1,119.41		$1,200.2590	$1,200.26	$1,200.30	$1,200.20