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	$190.30	9.635%	$208.6354	$208.64	$208.65	$208.60
Purchase #2	$85.97	4.626%	$89.947	$89.95	$89.95	$89.90
Purchase #3	$190.48	11.873%	$213.0957	$213.10	$213.10	$213.10
Purchase #4	$51.26	13.478%	$58.1688	$58.17	$58.15	$58.20
Purchase #5	$107.99	9.395%	$118.1357	$118.14	$118.15	$118.10
Purchase #6	$145.87	3.527%	$151.0148	$151.01	$151.00	$151.00
Purchase #7	$72.72	13.506%	$82.5416	$82.54	$82.55	$82.50
7 purchase totals =	$844.59		$921.5390	$921.55	$921.55	$921.40