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	$174.45	5.590%	$184.2018	$184.20	$184.20	$184.20
Purchase #2	$136.73	13.704%	$155.4675	$155.47	$155.45	$155.50
Purchase #3	$177.52	7.238%	$190.3689	$190.37	$190.35	$190.40
Purchase #4	$18.36	11.403%	$20.4536	$20.45	$20.45	$20.50
Purchase #5	$149.27	3.242%	$154.1093	$154.11	$154.10	$154.10
Purchase #6	$89.89	11.798%	$100.4952	$100.50	$100.50	$100.50
Purchase #7	$179.61	13.696%	$204.2094	$204.21	$204.20	$204.20
7 purchase totals =	$925.83		$1,009.3057	$1,009.31	$1,009.25	$1,009.40