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	$115.64	10.212%	$127.4492	$127.45	$127.45	$127.40
Purchase #2	$243.72	11.314%	$271.2945	$271.29	$271.30	$271.30
Purchase #3	$119.25	7.524%	$128.2224	$128.22	$128.20	$128.20
Purchase #4	$135.73	5.221%	$142.8165	$142.82	$142.80	$142.80
Purchase #5	$63.87	10.510%	$70.5827	$70.58	$70.60	$70.60
Purchase #6	$221.94	9.683%	$243.4305	$243.43	$243.45	$243.40
Purchase #7	$169.52	10.185%	$186.7856	$186.79	$186.80	$186.80
7 purchase totals =	$1,069.67		$1,170.5814	$1,170.58	$1,170.60	$1,170.50