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	$198.96	11.382%	$221.6056	$221.61	$221.60	$221.60
Purchase #2	$200.40	4.752%	$209.923	$209.92	$209.90	$209.90
Purchase #3	$184.77	6.305%	$196.4197	$196.42	$196.40	$196.40
Purchase #4	$101.44	4.396%	$105.8993	$105.90	$105.90	$105.90
Purchase #5	$178.75	5.481%	$188.5473	$188.55	$188.55	$188.50
Purchase #6	$201.51	10.867%	$223.4081	$223.41	$223.40	$223.40
Purchase #7	$10.50	4.115%	$10.9321	$10.93	$10.95	$10.90
7 purchase totals =	$1,076.33		$1,156.7351	$1,156.74	$1,156.70	$1,156.60