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	$144.50	4.159%	$150.5098	$150.51	$150.50	$150.50
Purchase #2	$183.47	5.435%	$193.4416	$193.44	$193.45	$193.40
Purchase #3	$218.61	11.417%	$243.5687	$243.57	$243.55	$243.60
Purchase #4	$169.51	5.798%	$179.3382	$179.34	$179.35	$179.30
Purchase #5	$64.52	4.256%	$67.266	$67.27	$67.25	$67.30
Purchase #6	$28.48	12.173%	$31.9469	$31.95	$31.95	$31.90
Purchase #7	$220.82	11.624%	$246.4881	$246.49	$246.50	$246.50
7 purchase totals =	$1,029.91		$1,112.5593	$1,112.57	$1,112.55	$1,112.50