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	$220.40	8.738%	$239.6586	$239.66	$239.65	$239.70
Purchase #2	$153.81	11.637%	$171.7089	$171.71	$171.70	$171.70
Purchase #3	$244.80	9.632%	$268.3791	$268.38	$268.40	$268.40
Purchase #4	$141.75	6.159%	$150.4804	$150.48	$150.50	$150.50
Purchase #5	$6.79	3.412%	$7.0217	$7.02	$7.00	$7.00
Purchase #6	$155.36	10.459%	$171.6091	$171.61	$171.60	$171.60
Purchase #7	$56.33	5.414%	$59.3797	$59.38	$59.40	$59.40
7 purchase totals =	$979.24		$1,068.2375	$1,068.24	$1,068.25	$1,068.30