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	$191.87	11.477%	$213.8909	$213.89	$213.90	$213.90
Purchase #2	$170.87	6.830%	$182.5404	$182.54	$182.55	$182.50
Purchase #3	$166.38	4.664%	$174.14	$174.14	$174.15	$174.10
Purchase #4	$182.96	9.815%	$200.9175	$200.92	$200.90	$200.90
Purchase #5	$72.29	9.109%	$78.8749	$78.87	$78.85	$78.90
Purchase #6	$99.83	11.865%	$111.6748	$111.67	$111.65	$111.70
Purchase #7	$234.87	5.161%	$246.9916	$246.99	$247.00	$247.00
7 purchase totals =	$1,119.07		$1,209.0301	$1,209.02	$1,209.00	$1,209.00