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	$11.54	11.416%	$12.8574	$12.86	$12.85	$12.90
Purchase #2	$45.54	3.588%	$47.174	$47.17	$47.15	$47.20
Purchase #3	$150.60	3.870%	$156.4282	$156.43	$156.45	$156.40
Purchase #4	$202.48	10.612%	$223.9672	$223.97	$223.95	$224.00
Purchase #5	$169.32	13.328%	$191.887	$191.89	$191.90	$191.90
Purchase #6	$147.46	5.187%	$155.1088	$155.11	$155.10	$155.10
Purchase #7	$249.72	12.654%	$281.3196	$281.32	$281.30	$281.30
7 purchase totals =	$976.66		$1,068.7422	$1,068.75	$1,068.70	$1,068.80