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	$158.99	8.256%	$172.1162	$172.12	$172.10	$172.10
Purchase #2	$48.33	12.445%	$54.3447	$54.34	$54.35	$54.30
Purchase #3	$197.75	12.775%	$223.0126	$223.01	$223.00	$223.00
Purchase #4	$231.63	8.591%	$251.5293	$251.53	$251.55	$251.50
Purchase #5	$210.50	13.182%	$238.2481	$238.25	$238.25	$238.20
Purchase #6	$101.96	3.227%	$105.2502	$105.25	$105.25	$105.30
Purchase #7	$111.77	7.683%	$120.3573	$120.36	$120.35	$120.40
7 purchase totals =	$1,060.93		$1,164.8584	$1,164.86	$1,164.85	$1,164.80