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	$72.46	8.450%	$78.5829	$78.58	$78.60	$78.60
Purchase #2	$55.63	11.728%	$62.1543	$62.15	$62.15	$62.20
Purchase #3	$85.89	13.566%	$97.5418	$97.54	$97.55	$97.50
Purchase #4	$134.98	13.315%	$152.9526	$152.95	$152.95	$153.00
Purchase #5	$154.56	9.378%	$169.0546	$169.05	$169.05	$169.10
Purchase #6	$151.32	6.608%	$161.3192	$161.32	$161.30	$161.30
Purchase #7	$38.55	13.190%	$43.6347	$43.63	$43.65	$43.60
7 purchase totals =	$693.39		$765.2401	$765.22	$765.25	$765.30