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	$89.31	6.681%	$95.2768	$95.28	$95.30	$95.30
Purchase #2	$123.70	11.607%	$138.0579	$138.06	$138.05	$138.10
Purchase #3	$176.71	5.171%	$185.8477	$185.85	$185.85	$185.80
Purchase #4	$56.68	5.114%	$59.5786	$59.58	$59.60	$59.60
Purchase #5	$174.29	11.392%	$194.1451	$194.15	$194.15	$194.10
Purchase #6	$157.25	7.269%	$168.6805	$168.68	$168.70	$168.70
Purchase #7	$34.98	10.464%	$38.6403	$38.64	$38.65	$38.60
7 purchase totals =	$812.92		$880.2269	$880.24	$880.30	$880.20