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	$19.36	13.281%	$21.9312	$21.93	$21.95	$21.90
Purchase #2	$28.99	7.344%	$31.119	$31.12	$31.10	$31.10
Purchase #3	$145.63	4.639%	$152.3858	$152.39	$152.40	$152.40
Purchase #4	$59.73	9.574%	$65.4486	$65.45	$65.45	$65.40
Purchase #5	$222.25	9.450%	$243.2526	$243.25	$243.25	$243.30
Purchase #6	$29.38	12.509%	$33.0551	$33.06	$33.05	$33.10
Purchase #7	$144.33	8.167%	$156.1174	$156.12	$156.10	$156.10
7 purchase totals =	$649.67		$703.3097	$703.32	$703.30	$703.30