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	$83.39	4.207%	$86.8982	$86.90	$86.90	$86.90
Purchase #2	$141.44	3.139%	$145.8798	$145.88	$145.90	$145.90
Purchase #3	$185.91	7.511%	$199.8737	$199.87	$199.85	$199.90
Purchase #4	$140.62	7.350%	$150.9556	$150.96	$150.95	$151.00
Purchase #5	$245.93	8.720%	$267.3751	$267.38	$267.40	$267.40
Purchase #6	$70.28	3.709%	$72.8867	$72.89	$72.90	$72.90
Purchase #7	$109.64	8.438%	$118.8914	$118.89	$118.90	$118.90
7 purchase totals =	$977.21		$1,042.7605	$1,042.77	$1,042.80	$1,042.90