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	$136.76	3.567%	$141.6382	$141.64	$141.65	$141.60
Purchase #2	$110.49	11.329%	$123.0074	$123.01	$123.00	$123.00
Purchase #3	$37.37	3.373%	$38.6305	$38.63	$38.65	$38.60
Purchase #4	$149.72	13.407%	$169.793	$169.79	$169.80	$169.80
Purchase #5	$166.65	3.349%	$172.2311	$172.23	$172.25	$172.20
Purchase #6	$75.81	3.262%	$78.2829	$78.28	$78.30	$78.30
Purchase #7	$17.97	8.759%	$19.544	$19.54	$19.55	$19.50
7 purchase totals =	$694.77		$743.1271	$743.12	$743.20	$743.00