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	$172.78	9.333%	$188.9056	$188.91	$188.90	$188.90
Purchase #2	$108.54	7.574%	$116.7608	$116.76	$116.75	$116.80
Purchase #3	$153.55	9.630%	$168.3369	$168.34	$168.35	$168.30
Purchase #4	$176.79	7.678%	$190.3639	$190.36	$190.35	$190.40
Purchase #5	$195.46	10.454%	$215.8934	$215.89	$215.90	$215.90
Purchase #6	$87.98	10.693%	$97.3877	$97.39	$97.40	$97.40
Purchase #7	$98.96	8.280%	$107.1539	$107.15	$107.15	$107.20
7 purchase totals =	$994.06		$1,084.8022	$1,084.80	$1,084.80	$1,084.90