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	$12.38	8.742%	$13.4623	$13.46	$13.45	$13.50
Purchase #2	$53.92	9.761%	$59.1831	$59.18	$59.20	$59.20
Purchase #3	$127.91	12.507%	$143.9077	$143.91	$143.90	$143.90
Purchase #4	$171.98	8.130%	$185.962	$185.96	$185.95	$186.00
Purchase #5	$204.67	8.137%	$221.324	$221.32	$221.30	$221.30
Purchase #6	$190.40	3.310%	$196.7022	$196.70	$196.70	$196.70
Purchase #7	$227.28	3.786%	$235.8848	$235.88	$235.90	$235.90
7 purchase totals =	$988.54		$1,056.4261	$1,056.41	$1,056.40	$1,056.50