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	$240.58	11.115%	$267.3205	$267.32	$267.30	$267.30
Purchase #2	$75.57	10.368%	$83.4051	$83.41	$83.40	$83.40
Purchase #3	$16.87	12.389%	$18.96	$18.96	$18.95	$19.00
Purchase #4	$74.41	10.593%	$82.2923	$82.29	$82.30	$82.30
Purchase #5	$200.37	5.505%	$211.4004	$211.40	$211.40	$211.40
Purchase #6	$198.48	12.552%	$223.3932	$223.39	$223.40	$223.40
Purchase #7	$134.40	11.851%	$150.3277	$150.33	$150.35	$150.30
7 purchase totals =	$940.68		$1,037.0992	$1,037.10	$1,037.10	$1,037.10