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	$240.93	9.777%	$264.4857	$264.49	$264.50	$264.50
Purchase #2	$86.33	5.484%	$91.0643	$91.06	$91.05	$91.10
Purchase #3	$235.88	12.850%	$266.1906	$266.19	$266.20	$266.20
Purchase #4	$179.44	4.711%	$187.8934	$187.89	$187.90	$187.90
Purchase #5	$193.37	3.804%	$200.7258	$200.73	$200.75	$200.70
Purchase #6	$134.90	3.326%	$139.3868	$139.39	$139.40	$139.40
Purchase #7	$35.81	3.526%	$37.0727	$37.07	$37.05	$37.10
7 purchase totals =	$1,106.66		$1,186.8193	$1,186.82	$1,186.85	$1,186.90