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	$69.54	3.620%	$72.0573	$72.06	$72.05	$72.10
Purchase #2	$27.68	8.825%	$30.1228	$30.12	$30.10	$30.10
Purchase #3	$55.82	10.264%	$61.5494	$61.55	$61.55	$61.50
Purchase #4	$176.85	3.163%	$182.4438	$182.44	$182.45	$182.40
Purchase #5	$80.36	11.426%	$89.5419	$89.54	$89.55	$89.50
Purchase #6	$182.54	9.711%	$200.2665	$200.27	$200.25	$200.30
Purchase #7	$108.43	8.739%	$117.9057	$117.91	$117.90	$117.90
7 purchase totals =	$701.22		$753.8874	$753.89	$753.85	$753.80