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	$221.51	6.191%	$235.2237	$235.22	$235.20	$235.20
Purchase #2	$45.61	4.841%	$47.818	$47.82	$47.80	$47.80
Purchase #3	$95.56	8.544%	$103.7246	$103.72	$103.70	$103.70
Purchase #4	$5.36	8.380%	$5.8092	$5.81	$5.80	$5.80
Purchase #5	$132.46	11.865%	$148.1764	$148.18	$148.20	$148.20
Purchase #6	$162.40	3.540%	$168.149	$168.15	$168.15	$168.10
Purchase #7	$89.32	10.330%	$98.5468	$98.55	$98.55	$98.50
7 purchase totals =	$752.22		$807.4477	$807.45	$807.40	$807.30