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	$181.41	8.329%	$196.5196	$196.52	$196.50	$196.50
Purchase #2	$145.89	4.323%	$152.1968	$152.20	$152.20	$152.20
Purchase #3	$22.47	12.264%	$25.2257	$25.23	$25.25	$25.20
Purchase #4	$56.46	11.685%	$63.0574	$63.06	$63.05	$63.10
Purchase #5	$139.59	7.471%	$150.0188	$150.02	$150.00	$150.00
Purchase #6	$206.65	8.107%	$223.4031	$223.40	$223.40	$223.40
Purchase #7	$33.89	11.233%	$37.6969	$37.70	$37.70	$37.70
7 purchase totals =	$786.36		$848.1183	$848.13	$848.10	$848.10