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	$247.40	6.333%	$263.0678	$263.07	$263.05	$263.10
Purchase #2	$52.55	4.579%	$54.9563	$54.96	$54.95	$55.00
Purchase #3	$27.95	13.749%	$31.7928	$31.79	$31.80	$31.80
Purchase #4	$233.86	8.383%	$253.4645	$253.46	$253.45	$253.50
Purchase #5	$134.43	12.713%	$151.5201	$151.52	$151.50	$151.50
Purchase #6	$248.87	9.830%	$273.3339	$273.33	$273.35	$273.30
Purchase #7	$40.93	10.209%	$45.1085	$45.11	$45.10	$45.10
7 purchase totals =	$985.99		$1,073.2439	$1,073.24	$1,073.20	$1,073.30