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	$201.34	10.522%	$222.525	$222.53	$222.55	$222.50
Purchase #2	$210.78	12.629%	$237.3994	$237.40	$237.40	$237.40
Purchase #3	$101.70	7.524%	$109.3519	$109.35	$109.35	$109.40
Purchase #4	$174.80	12.400%	$196.4752	$196.48	$196.50	$196.50
Purchase #5	$101.86	4.451%	$106.3938	$106.39	$106.40	$106.40
Purchase #6	$151.40	10.778%	$167.7179	$167.72	$167.70	$167.70
Purchase #7	$149.53	9.674%	$163.9955	$164.00	$164.00	$164.00
7 purchase totals =	$1,091.41		$1,203.8587	$1,203.87	$1,203.90	$1,203.90