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	$134.73	11.352%	$150.0245	$150.02	$150.00	$150.00
Purchase #2	$105.32	13.275%	$119.3012	$119.30	$119.30	$119.30
Purchase #3	$43.40	9.589%	$47.5616	$47.56	$47.55	$47.60
Purchase #4	$41.80	12.298%	$46.9406	$46.94	$46.95	$46.90
Purchase #5	$181.72	7.252%	$194.8983	$194.90	$194.90	$194.90
Purchase #6	$215.68	8.162%	$233.2838	$233.28	$233.30	$233.30
Purchase #7	$159.67	5.801%	$168.9325	$168.93	$168.95	$168.90
7 purchase totals =	$882.32		$960.9425	$960.93	$960.95	$960.90