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	$129.76	9.563%	$142.1689	$142.17	$142.15	$142.20
Purchase #2	$44.66	13.672%	$50.7659	$50.77	$50.75	$50.80
Purchase #3	$75.57	6.411%	$80.4148	$80.41	$80.40	$80.40
Purchase #4	$167.33	10.853%	$185.4903	$185.49	$185.50	$185.50
Purchase #5	$196.34	5.399%	$206.9404	$206.94	$206.95	$206.90
Purchase #6	$213.80	6.474%	$227.6414	$227.64	$227.65	$227.60
Purchase #7	$110.25	7.490%	$118.5077	$118.51	$118.50	$118.50
7 purchase totals =	$937.71		$1,011.9294	$1,011.93	$1,011.90	$1,011.90