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	$215.90	5.583%	$227.9537	$227.95	$227.95	$228.00
Purchase #2	$204.74	5.155%	$215.2943	$215.29	$215.30	$215.30
Purchase #3	$105.66	9.541%	$115.741	$115.74	$115.75	$115.70
Purchase #4	$80.29	12.597%	$90.4041	$90.40	$90.40	$90.40
Purchase #5	$233.51	5.542%	$246.4511	$246.45	$246.45	$246.50
Purchase #6	$158.39	6.308%	$168.3812	$168.38	$168.40	$168.40
Purchase #7	$191.33	10.214%	$210.8724	$210.87	$210.85	$210.90
7 purchase totals =	$1,189.82		$1,275.0978	$1,275.08	$1,275.10	$1,275.20