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	$43.25	7.792%	$46.62	$46.62	$46.60	$46.60
Purchase #2	$84.39	13.696%	$95.9481	$95.95	$95.95	$95.90
Purchase #3	$165.57	3.573%	$171.4858	$171.49	$171.50	$171.50
Purchase #4	$242.80	7.860%	$261.8841	$261.88	$261.90	$261.90
Purchase #5	$142.73	3.180%	$147.2688	$147.27	$147.25	$147.30
Purchase #6	$199.89	3.320%	$206.5263	$206.53	$206.55	$206.50
Purchase #7	$139.34	4.505%	$145.6173	$145.62	$145.60	$145.60
7 purchase totals =	$1,017.97		$1,075.3504	$1,075.36	$1,075.35	$1,075.30