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	$147.44	11.420%	$164.2776	$164.28	$164.30	$164.30
Purchase #2	$59.67	5.512%	$62.959	$62.96	$62.95	$63.00
Purchase #3	$30.32	5.652%	$32.0337	$32.03	$32.05	$32.00
Purchase #4	$42.48	6.683%	$45.3189	$45.32	$45.30	$45.30
Purchase #5	$180.41	3.290%	$186.3455	$186.35	$186.35	$186.30
Purchase #6	$28.35	10.272%	$31.2621	$31.26	$31.25	$31.30
Purchase #7	$247.52	12.677%	$278.8981	$278.90	$278.90	$278.90
7 purchase totals =	$736.19		$801.0949	$801.10	$801.10	$801.10