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	$63.79	6.356%	$67.8445	$67.84	$67.85	$67.80
Purchase #2	$206.72	7.723%	$222.685	$222.69	$222.70	$222.70
Purchase #3	$229.92	4.236%	$239.6594	$239.66	$239.65	$239.70
Purchase #4	$141.40	7.768%	$152.384	$152.38	$152.40	$152.40
Purchase #5	$159.80	3.509%	$165.4074	$165.41	$165.40	$165.40
Purchase #6	$74.61	5.639%	$78.8173	$78.82	$78.80	$78.80
Purchase #7	$80.59	6.270%	$85.643	$85.64	$85.65	$85.60
7 purchase totals =	$956.83		$1,012.4406	$1,012.44	$1,012.45	$1,012.40