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	$121.88	9.307%	$133.2234	$133.22	$133.20	$133.20
Purchase #2	$113.73	9.864%	$124.9483	$124.95	$124.95	$124.90
Purchase #3	$191.48	6.640%	$204.1943	$204.19	$204.20	$204.20
Purchase #4	$39.43	3.444%	$40.788	$40.79	$40.80	$40.80
Purchase #5	$187.29	4.855%	$196.3829	$196.38	$196.40	$196.40
Purchase #6	$211.58	12.577%	$238.1904	$238.19	$238.20	$238.20
Purchase #7	$76.34	11.419%	$85.0573	$85.06	$85.05	$85.10
7 purchase totals =	$941.73		$1,022.7846	$1,022.78	$1,022.80	$1,022.80