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	$32.30	8.811%	$35.146	$35.15	$35.15	$35.10
Purchase #2	$220.32	6.351%	$234.3125	$234.31	$234.30	$234.30
Purchase #3	$47.61	9.404%	$52.0872	$52.09	$52.10	$52.10
Purchase #4	$250.97	6.857%	$268.179	$268.18	$268.20	$268.20
Purchase #5	$140.74	3.265%	$145.3352	$145.34	$145.35	$145.30
Purchase #6	$53.60	10.691%	$59.3304	$59.33	$59.35	$59.30
Purchase #7	$201.37	4.575%	$210.5827	$210.58	$210.60	$210.60
7 purchase totals =	$946.91		$1,004.9730	$1,004.98	$1,005.05	$1,004.90