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	$98.59	10.639%	$109.079	$109.08	$109.10	$109.10
Purchase #2	$176.30	11.732%	$196.9835	$196.98	$197.00	$197.00
Purchase #3	$137.32	4.825%	$143.9457	$143.95	$143.95	$143.90
Purchase #4	$37.48	7.159%	$40.1632	$40.16	$40.15	$40.20
Purchase #5	$246.27	13.196%	$278.7678	$278.77	$278.75	$278.80
Purchase #6	$50.26	7.326%	$53.942	$53.94	$53.95	$53.90
Purchase #7	$176.26	4.615%	$184.3944	$184.39	$184.40	$184.40
7 purchase totals =	$922.48		$1,007.2756	$1,007.27	$1,007.30	$1,007.30