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	$236.74	7.255%	$253.9155	$253.92	$253.90	$253.90
Purchase #2	$29.31	8.255%	$31.7295	$31.73	$31.75	$31.70
Purchase #3	$111.84	8.520%	$121.3688	$121.37	$121.35	$121.40
Purchase #4	$71.93	12.476%	$80.904	$80.90	$80.90	$80.90
Purchase #5	$70.54	10.601%	$78.0179	$78.02	$78.00	$78.00
Purchase #6	$249.88	5.507%	$263.6409	$263.64	$263.65	$263.60
Purchase #7	$96.45	8.155%	$104.3155	$104.32	$104.30	$104.30
7 purchase totals =	$866.69		$933.8921	$933.90	$933.85	$933.80