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	$147.72	5.353%	$155.6275	$155.63	$155.65	$155.60
Purchase #2	$133.77	3.767%	$138.8091	$138.81	$138.80	$138.80
Purchase #3	$79.79	11.604%	$89.0488	$89.05	$89.05	$89.00
Purchase #4	$194.47	8.484%	$210.9688	$210.97	$210.95	$211.00
Purchase #5	$211.89	12.413%	$238.1919	$238.19	$238.20	$238.20
Purchase #6	$78.96	4.294%	$82.3505	$82.35	$82.35	$82.40
Purchase #7	$163.41	5.176%	$171.8681	$171.87	$171.85	$171.90
7 purchase totals =	$1,010.01		$1,086.8647	$1,086.87	$1,086.85	$1,086.90