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	$50.25	8.323%	$54.4323	$54.43	$54.45	$54.40
Purchase #2	$71.59	9.373%	$78.3001	$78.30	$78.30	$78.30
Purchase #3	$168.99	13.372%	$191.5873	$191.59	$191.60	$191.60
Purchase #4	$184.48	11.713%	$206.0881	$206.09	$206.10	$206.10
Purchase #5	$79.31	8.625%	$86.1505	$86.15	$86.15	$86.20
Purchase #6	$189.64	13.129%	$214.5378	$214.54	$214.55	$214.50
Purchase #7	$144.38	12.430%	$162.3264	$162.33	$162.35	$162.30
7 purchase totals =	$888.64		$993.4225	$993.43	$993.50	$993.40