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	$111.90	5.816%	$118.4081	$118.41	$118.40	$118.40
Purchase #2	$75.58	3.647%	$78.3364	$78.34	$78.35	$78.30
Purchase #3	$42.47	8.503%	$46.0812	$46.08	$46.10	$46.10
Purchase #4	$237.37	13.847%	$270.2386	$270.24	$270.25	$270.20
Purchase #5	$99.75	9.771%	$109.4966	$109.50	$109.50	$109.50
Purchase #6	$119.54	12.517%	$134.5028	$134.50	$134.50	$134.50
Purchase #7	$204.36	12.431%	$229.764	$229.76	$229.75	$229.80
7 purchase totals =	$890.97		$986.8277	$986.83	$986.85	$986.80