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	$233.45	12.856%	$263.4623	$263.46	$263.45	$263.50
Purchase #2	$164.28	13.339%	$186.1933	$186.19	$186.20	$186.20
Purchase #3	$55.47	7.845%	$59.8216	$59.82	$59.80	$59.80
Purchase #4	$99.51	11.612%	$111.0651	$111.07	$111.05	$111.10
Purchase #5	$82.34	4.460%	$86.0124	$86.01	$86.00	$86.00
Purchase #6	$61.39	9.795%	$67.4032	$67.40	$67.40	$67.40
Purchase #7	$250.55	10.585%	$277.0707	$277.07	$277.05	$277.10
7 purchase totals =	$946.99		$1,051.0286	$1,051.02	$1,050.95	$1,051.10