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	$136.50	13.833%	$155.382	$155.38	$155.40	$155.40
Purchase #2	$32.40	13.698%	$36.8382	$36.84	$36.85	$36.80
Purchase #3	$239.66	13.570%	$272.1819	$272.18	$272.20	$272.20
Purchase #4	$152.98	12.365%	$171.896	$171.90	$171.90	$171.90
Purchase #5	$202.84	3.307%	$209.5479	$209.55	$209.55	$209.50
Purchase #6	$64.56	10.542%	$71.3659	$71.37	$71.35	$71.40
Purchase #7	$148.41	5.736%	$156.9228	$156.92	$156.90	$156.90
7 purchase totals =	$977.35		$1,074.1347	$1,074.14	$1,074.15	$1,074.10