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	$225.81	10.792%	$250.1794	$250.18	$250.20	$250.20
Purchase #2	$53.80	7.552%	$57.863	$57.86	$57.85	$57.90
Purchase #3	$115.56	10.469%	$127.658	$127.66	$127.65	$127.70
Purchase #4	$109.94	4.323%	$114.6927	$114.69	$114.70	$114.70
Purchase #5	$82.68	10.648%	$91.4838	$91.48	$91.50	$91.50
Purchase #6	$58.88	12.379%	$66.1688	$66.17	$66.15	$66.20
Purchase #7	$208.57	12.363%	$234.3555	$234.36	$234.35	$234.40
7 purchase totals =	$855.24		$942.4012	$942.40	$942.40	$942.60