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	$190.99	5.701%	$201.8783	$201.88	$201.90	$201.90
Purchase #2	$128.54	12.705%	$144.871	$144.87	$144.85	$144.90
Purchase #3	$56.60	4.648%	$59.2308	$59.23	$59.25	$59.20
Purchase #4	$189.50	12.744%	$213.6499	$213.65	$213.65	$213.60
Purchase #5	$37.69	8.260%	$40.8032	$40.80	$40.80	$40.80
Purchase #6	$106.89	11.762%	$119.4624	$119.46	$119.45	$119.50
Purchase #7	$243.27	13.308%	$275.6444	$275.64	$275.65	$275.60
7 purchase totals =	$953.48		$1,055.5400	$1,055.53	$1,055.55	$1,055.50