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	$220.92	3.663%	$229.0123	$229.01	$229.00	$229.00
Purchase #2	$131.76	11.505%	$146.919	$146.92	$146.90	$146.90
Purchase #3	$97.91	3.589%	$101.424	$101.42	$101.40	$101.40
Purchase #4	$71.59	6.736%	$76.4123	$76.41	$76.40	$76.40
Purchase #5	$241.57	7.599%	$259.9269	$259.93	$259.95	$259.90
Purchase #6	$72.31	5.167%	$76.0463	$76.05	$76.05	$76.00
Purchase #7	$117.72	9.396%	$128.781	$128.78	$128.80	$128.80
7 purchase totals =	$953.78		$1,018.5218	$1,018.52	$1,018.50	$1,018.40