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	$46.45	3.524%	$48.0869	$48.09	$48.10	$48.10
Purchase #2	$176.63	5.241%	$185.8872	$185.89	$185.90	$185.90
Purchase #3	$26.74	6.577%	$28.4987	$28.50	$28.50	$28.50
Purchase #4	$131.33	9.351%	$143.6107	$143.61	$143.60	$143.60
Purchase #5	$65.25	8.635%	$70.8843	$70.88	$70.90	$70.90
Purchase #6	$193.46	6.231%	$205.5145	$205.51	$205.50	$205.50
Purchase #7	$29.52	6.166%	$31.3402	$31.34	$31.35	$31.30
7 purchase totals =	$669.38		$713.8225	$713.82	$713.85	$713.80