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	$81.65	5.523%	$86.1595	$86.16	$86.15	$86.20
Purchase #2	$70.25	11.418%	$78.2711	$78.27	$78.25	$78.30
Purchase #3	$244.26	8.440%	$264.8755	$264.88	$264.90	$264.90
Purchase #4	$193.77	3.109%	$199.7943	$199.79	$199.80	$199.80
Purchase #5	$19.90	6.740%	$21.2413	$21.24	$21.25	$21.20
Purchase #6	$169.92	7.840%	$183.2417	$183.24	$183.25	$183.20
Purchase #7	$81.58	13.484%	$92.5802	$92.58	$92.60	$92.60
7 purchase totals =	$861.33		$926.1636	$926.16	$926.20	$926.20