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	$118.84	10.708%	$131.5654	$131.57	$131.55	$131.60
Purchase #2	$53.85	6.168%	$57.1715	$57.17	$57.15	$57.20
Purchase #3	$141.30	6.335%	$150.2514	$150.25	$150.25	$150.30
Purchase #4	$231.44	13.374%	$262.3928	$262.39	$262.40	$262.40
Purchase #5	$173.71	3.718%	$180.1685	$180.17	$180.15	$180.20
Purchase #6	$105.72	9.384%	$115.6408	$115.64	$115.65	$115.60
Purchase #7	$179.40	11.871%	$200.6966	$200.70	$200.70	$200.70
7 purchase totals =	$1,004.26		$1,097.8870	$1,097.89	$1,097.85	$1,098.00