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	$198.73	6.295%	$211.2401	$211.24	$211.25	$211.20
Purchase #2	$33.72	6.864%	$36.0345	$36.03	$36.05	$36.00
Purchase #3	$30.30	6.844%	$32.3737	$32.37	$32.35	$32.40
Purchase #4	$68.94	13.433%	$78.2007	$78.20	$78.20	$78.20
Purchase #5	$244.75	13.719%	$278.3273	$278.33	$278.35	$278.30
Purchase #6	$25.48	9.305%	$27.8509	$27.85	$27.85	$27.90
Purchase #7	$12.32	4.654%	$12.8934	$12.89	$12.90	$12.90
7 purchase totals =	$614.24		$676.9206	$676.91	$676.95	$676.90