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	$119.30	6.802%	$127.4148	$127.41	$127.40	$127.40
Purchase #2	$41.48	6.209%	$44.0555	$44.06	$44.05	$44.10
Purchase #3	$200.25	11.539%	$223.3568	$223.36	$223.35	$223.40
Purchase #4	$92.33	13.543%	$104.8343	$104.83	$104.85	$104.80
Purchase #5	$141.78	12.478%	$159.4713	$159.47	$159.45	$159.50
Purchase #6	$146.97	5.529%	$155.096	$155.10	$155.10	$155.10
Purchase #7	$128.88	3.600%	$133.5197	$133.52	$133.50	$133.50
7 purchase totals =	$870.99		$947.7484	$947.75	$947.70	$947.80