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	$62.97	7.282%	$67.5555	$67.56	$67.55	$67.60
Purchase #2	$51.57	6.780%	$55.0664	$55.07	$55.05	$55.10
Purchase #3	$67.92	8.660%	$73.8019	$73.80	$73.80	$73.80
Purchase #4	$75.51	3.441%	$78.1083	$78.11	$78.10	$78.10
Purchase #5	$105.90	12.427%	$119.0602	$119.06	$119.05	$119.10
Purchase #6	$173.64	6.597%	$185.095	$185.10	$185.10	$185.10
Purchase #7	$189.81	8.137%	$205.2548	$205.25	$205.25	$205.30
7 purchase totals =	$727.32		$783.9421	$783.95	$783.90	$784.10