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	$180.38	9.103%	$196.8	$196.80	$196.80	$196.80
Purchase #2	$99.43	3.864%	$103.272	$103.27	$103.25	$103.30
Purchase #3	$99.48	13.839%	$113.247	$113.25	$113.25	$113.20
Purchase #4	$189.71	12.776%	$213.9473	$213.95	$213.95	$213.90
Purchase #5	$62.83	11.752%	$70.2138	$70.21	$70.20	$70.20
Purchase #6	$231.76	5.230%	$243.881	$243.88	$243.90	$243.90
Purchase #7	$158.74	13.825%	$180.6858	$180.69	$180.70	$180.70
7 purchase totals =	$1,022.33		$1,122.0469	$1,122.05	$1,122.05	$1,122.00