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	$52.92	3.834%	$54.949	$54.95	$54.95	$54.90
Purchase #2	$210.86	13.108%	$238.4995	$238.50	$238.50	$238.50
Purchase #3	$67.72	7.820%	$73.0157	$73.02	$73.00	$73.00
Purchase #4	$133.31	13.579%	$151.4122	$151.41	$151.40	$151.40
Purchase #5	$203.66	12.323%	$228.757	$228.76	$228.75	$228.80
Purchase #6	$9.46	11.319%	$10.5308	$10.53	$10.55	$10.50
Purchase #7	$183.38	7.369%	$196.8933	$196.89	$196.90	$196.90
7 purchase totals =	$861.31		$954.0575	$954.06	$954.05	$954.00