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	$205.68	8.250%	$222.6486	$222.65	$222.65	$222.60
Purchase #2	$62.60	6.554%	$66.7028	$66.70	$66.70	$66.70
Purchase #3	$81.61	9.461%	$89.3311	$89.33	$89.35	$89.30
Purchase #4	$33.84	4.230%	$35.2714	$35.27	$35.25	$35.30
Purchase #5	$72.77	12.487%	$81.8568	$81.86	$81.85	$81.90
Purchase #6	$168.63	10.484%	$186.3092	$186.31	$186.30	$186.30
Purchase #7	$224.33	8.331%	$243.0189	$243.02	$243.00	$243.00
7 purchase totals =	$849.46		$925.1388	$925.14	$925.10	$925.10