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	$164.31	13.460%	$186.4261	$186.43	$186.45	$186.40
Purchase #2	$172.85	4.850%	$181.2332	$181.23	$181.25	$181.20
Purchase #3	$237.49	4.590%	$248.3908	$248.39	$248.40	$248.40
Purchase #4	$78.68	5.608%	$83.0924	$83.09	$83.10	$83.10
Purchase #5	$93.56	6.354%	$99.5048	$99.50	$99.50	$99.50
Purchase #6	$199.51	5.556%	$210.5948	$210.59	$210.60	$210.60
Purchase #7	$209.81	7.305%	$225.1366	$225.14	$225.15	$225.10
7 purchase totals =	$1,156.21		$1,234.3787	$1,234.37	$1,234.45	$1,234.30