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	$234.40	13.249%	$265.4557	$265.46	$265.45	$265.50
Purchase #2	$54.71	3.152%	$56.4345	$56.43	$56.45	$56.40
Purchase #3	$195.65	7.827%	$210.9635	$210.96	$210.95	$211.00
Purchase #4	$91.32	13.795%	$103.9176	$103.92	$103.90	$103.90
Purchase #5	$49.88	6.722%	$53.2329	$53.23	$53.25	$53.20
Purchase #6	$136.80	3.218%	$141.2022	$141.20	$141.20	$141.20
Purchase #7	$191.44	9.661%	$209.935	$209.94	$209.95	$209.90
7 purchase totals =	$954.20		$1,041.1414	$1,041.14	$1,041.15	$1,041.10