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	$69.98	8.198%	$75.717	$75.72	$75.70	$75.70
Purchase #2	$168.75	6.320%	$179.415	$179.42	$179.40	$179.40
Purchase #3	$70.34	12.172%	$78.9018	$78.90	$78.90	$78.90
Purchase #4	$215.84	5.658%	$228.0522	$228.05	$228.05	$228.10
Purchase #5	$85.98	4.382%	$89.7476	$89.75	$89.75	$89.70
Purchase #6	$137.76	9.439%	$150.7632	$150.76	$150.75	$150.80
Purchase #7	$194.73	7.535%	$209.4029	$209.40	$209.40	$209.40
7 purchase totals =	$943.38		$1,011.9997	$1,012.00	$1,011.95	$1,012.00