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	$72.60	8.332%	$78.649	$78.65	$78.65	$78.60
Purchase #2	$10.79	4.121%	$11.2347	$11.23	$11.25	$11.20
Purchase #3	$80.81	6.517%	$86.0764	$86.08	$86.10	$86.10
Purchase #4	$51.77	9.820%	$56.8538	$56.85	$56.85	$56.90
Purchase #5	$201.67	4.860%	$211.4712	$211.47	$211.45	$211.50
Purchase #6	$79.81	12.711%	$89.9546	$89.95	$89.95	$90.00
Purchase #7	$84.76	13.314%	$96.0449	$96.04	$96.05	$96.00
7 purchase totals =	$582.21		$630.2846	$630.27	$630.30	$630.30