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	$57.58	3.269%	$59.4623	$59.46	$59.45	$59.50
Purchase #2	$238.90	12.585%	$268.9656	$268.97	$268.95	$269.00
Purchase #3	$84.53	12.119%	$94.7742	$94.77	$94.75	$94.80
Purchase #4	$238.46	12.501%	$268.2699	$268.27	$268.25	$268.30
Purchase #5	$65.31	6.407%	$69.4944	$69.49	$69.50	$69.50
Purchase #6	$154.84	3.264%	$159.894	$159.89	$159.90	$159.90
Purchase #7	$128.97	9.507%	$141.2312	$141.23	$141.25	$141.20
7 purchase totals =	$968.59		$1,062.0916	$1,062.08	$1,062.05	$1,062.20