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	$78.94	9.319%	$86.2964	$86.30	$86.30	$86.30
Purchase #2	$65.29	10.356%	$72.0514	$72.05	$72.05	$72.10
Purchase #3	$38.79	12.623%	$43.6865	$43.69	$43.70	$43.70
Purchase #4	$95.35	13.587%	$108.3052	$108.31	$108.30	$108.30
Purchase #5	$155.41	6.514%	$165.5334	$165.53	$165.55	$165.50
Purchase #6	$114.99	11.556%	$128.2782	$128.28	$128.30	$128.30
Purchase #7	$235.71	5.323%	$248.2568	$248.26	$248.25	$248.30
7 purchase totals =	$784.48		$852.4079	$852.42	$852.45	$852.50