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	$235.51	5.283%	$247.952	$247.95	$247.95	$248.00
Purchase #2	$164.48	4.539%	$171.9457	$171.95	$171.95	$171.90
Purchase #3	$219.32	13.842%	$249.6783	$249.68	$249.70	$249.70
Purchase #4	$68.71	13.369%	$77.8958	$77.90	$77.90	$77.90
Purchase #5	$48.40	12.458%	$54.4297	$54.43	$54.45	$54.40
Purchase #6	$170.83	5.771%	$180.6886	$180.69	$180.70	$180.70
Purchase #7	$39.98	7.362%	$42.9233	$42.92	$42.90	$42.90
7 purchase totals =	$947.23		$1,025.5134	$1,025.52	$1,025.55	$1,025.50