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	$159.80	10.398%	$176.416	$176.42	$176.40	$176.40
Purchase #2	$99.35	13.618%	$112.8795	$112.88	$112.90	$112.90
Purchase #3	$219.84	10.564%	$243.0639	$243.06	$243.05	$243.10
Purchase #4	$95.31	10.751%	$105.5568	$105.56	$105.55	$105.60
Purchase #5	$140.63	10.608%	$155.548	$155.55	$155.55	$155.50
Purchase #6	$162.25	8.496%	$176.0348	$176.03	$176.05	$176.00
Purchase #7	$141.41	3.867%	$146.8783	$146.88	$146.90	$146.90
7 purchase totals =	$1,018.59		$1,116.3773	$1,116.38	$1,116.40	$1,116.40