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	$167.57	4.386%	$174.9196	$174.92	$174.90	$174.90
Purchase #2	$183.40	4.854%	$192.3022	$192.30	$192.30	$192.30
Purchase #3	$197.35	13.159%	$223.3193	$223.32	$223.30	$223.30
Purchase #4	$230.93	12.821%	$260.5375	$260.54	$260.55	$260.50
Purchase #5	$240.73	9.859%	$264.4636	$264.46	$264.45	$264.50
Purchase #6	$185.88	5.671%	$196.4213	$196.42	$196.40	$196.40
Purchase #7	$11.61	13.334%	$13.1581	$13.16	$13.15	$13.20
7 purchase totals =	$1,217.47		$1,325.1216	$1,325.12	$1,325.05	$1,325.10