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	$200.92	9.292%	$219.5895	$219.59	$219.60	$219.60
Purchase #2	$83.88	3.202%	$86.5658	$86.57	$86.55	$86.60
Purchase #3	$165.98	9.418%	$181.612	$181.61	$181.60	$181.60
Purchase #4	$136.76	10.801%	$151.5314	$151.53	$151.55	$151.50
Purchase #5	$97.67	11.521%	$108.9226	$108.92	$108.90	$108.90
Purchase #6	$30.73	7.764%	$33.1159	$33.12	$33.10	$33.10
Purchase #7	$171.46	10.639%	$189.7016	$189.70	$189.70	$189.70
7 purchase totals =	$887.40		$971.0388	$971.04	$971.00	$971.00