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	$157.95	13.524%	$179.3112	$179.31	$179.30	$179.30
Purchase #2	$72.85	7.145%	$78.0551	$78.06	$78.05	$78.10
Purchase #3	$234.94	6.626%	$250.5071	$250.51	$250.50	$250.50
Purchase #4	$64.92	3.846%	$67.4168	$67.42	$67.40	$67.40
Purchase #5	$140.41	6.611%	$149.6925	$149.69	$149.70	$149.70
Purchase #6	$191.62	7.151%	$205.3227	$205.32	$205.30	$205.30
Purchase #7	$54.68	3.673%	$56.6884	$56.69	$56.70	$56.70
7 purchase totals =	$917.37		$986.9938	$987.00	$986.95	$987.00