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	$32.72	5.321%	$34.461	$34.46	$34.45	$34.50
Purchase #2	$82.63	3.818%	$85.7848	$85.78	$85.80	$85.80
Purchase #3	$136.35	11.503%	$152.0343	$152.03	$152.05	$152.00
Purchase #4	$210.32	12.203%	$235.9853	$235.99	$236.00	$236.00
Purchase #5	$93.69	8.294%	$101.4606	$101.46	$101.45	$101.50
Purchase #6	$120.82	8.789%	$131.4389	$131.44	$131.45	$131.40
Purchase #7	$166.53	11.148%	$185.0948	$185.09	$185.10	$185.10
7 purchase totals =	$843.06		$926.2597	$926.25	$926.30	$926.30