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	$108.79	6.298%	$115.6416	$115.64	$115.65	$115.60
Purchase #2	$216.49	12.616%	$243.8024	$243.80	$243.80	$243.80
Purchase #3	$140.48	5.721%	$148.5169	$148.52	$148.50	$148.50
Purchase #4	$114.58	4.544%	$119.7865	$119.79	$119.80	$119.80
Purchase #5	$120.76	9.120%	$131.7733	$131.77	$131.75	$131.80
Purchase #6	$136.50	11.668%	$152.4268	$152.43	$152.45	$152.40
Purchase #7	$227.27	5.732%	$240.2971	$240.30	$240.30	$240.30
7 purchase totals =	$1,064.87		$1,152.2446	$1,152.25	$1,152.25	$1,152.20