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	$72.59	13.270%	$82.2227	$82.22	$82.20	$82.20
Purchase #2	$92.73	3.377%	$95.8615	$95.86	$95.85	$95.90
Purchase #3	$141.98	9.250%	$155.1132	$155.11	$155.10	$155.10
Purchase #4	$83.34	10.263%	$91.8932	$91.89	$91.90	$91.90
Purchase #5	$155.33	13.149%	$175.7543	$175.75	$175.75	$175.80
Purchase #6	$178.72	9.766%	$196.1738	$196.17	$196.15	$196.20
Purchase #7	$247.96	12.459%	$278.8533	$278.85	$278.85	$278.90
7 purchase totals =	$972.65		$1,075.8720	$1,075.85	$1,075.80	$1,076.00