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	$215.76	4.290%	$225.0161	$225.02	$225.00	$225.00
Purchase #2	$86.39	11.430%	$96.2644	$96.26	$96.25	$96.30
Purchase #3	$151.77	13.262%	$171.8977	$171.90	$171.90	$171.90
Purchase #4	$185.67	13.595%	$210.9118	$210.91	$210.90	$210.90
Purchase #5	$249.84	8.402%	$270.8316	$270.83	$270.85	$270.80
Purchase #6	$39.82	3.159%	$41.0779	$41.08	$41.10	$41.10
Purchase #7	$123.83	3.557%	$128.2346	$128.23	$128.25	$128.20
7 purchase totals =	$1,053.08		$1,144.2341	$1,144.23	$1,144.25	$1,144.20