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	$147.82	10.637%	$163.5436	$163.54	$163.55	$163.50
Purchase #2	$74.41	11.387%	$82.8831	$82.88	$82.90	$82.90
Purchase #3	$235.89	13.320%	$267.3105	$267.31	$267.30	$267.30
Purchase #4	$176.71	6.283%	$187.8127	$187.81	$187.80	$187.80
Purchase #5	$39.52	8.594%	$42.9163	$42.92	$42.90	$42.90
Purchase #6	$102.92	6.666%	$109.7806	$109.78	$109.80	$109.80
Purchase #7	$92.65	7.195%	$99.3162	$99.32	$99.30	$99.30
7 purchase totals =	$869.92		$953.5630	$953.56	$953.55	$953.50