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	$86.37	10.617%	$95.5399	$95.54	$95.55	$95.50
Purchase #2	$155.50	7.610%	$167.3336	$167.33	$167.35	$167.30
Purchase #3	$133.47	3.871%	$138.6366	$138.64	$138.65	$138.60
Purchase #4	$76.43	3.131%	$78.823	$78.82	$78.80	$78.80
Purchase #5	$248.41	6.112%	$263.5928	$263.59	$263.60	$263.60
Purchase #6	$192.42	7.122%	$206.1242	$206.12	$206.10	$206.10
Purchase #7	$120.77	7.874%	$130.2794	$130.28	$130.30	$130.30
7 purchase totals =	$1,013.37		$1,080.3295	$1,080.32	$1,080.35	$1,080.20