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	$62.25	13.682%	$70.767	$70.77	$70.75	$70.80
Purchase #2	$233.76	6.745%	$249.5271	$249.53	$249.55	$249.50
Purchase #3	$189.61	3.414%	$196.0833	$196.08	$196.10	$196.10
Purchase #4	$6.96	12.160%	$7.8063	$7.81	$7.80	$7.80
Purchase #5	$184.31	4.170%	$191.9957	$192.00	$192.00	$192.00
Purchase #6	$110.53	5.302%	$116.3903	$116.39	$116.40	$116.40
Purchase #7	$170.52	7.500%	$183.309	$183.31	$183.30	$183.30
7 purchase totals =	$957.94		$1,015.8787	$1,015.89	$1,015.90	$1,015.90