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	$176.56	6.177%	$187.4661	$187.47	$187.45	$187.50
Purchase #2	$128.26	3.172%	$132.3284	$132.33	$132.35	$132.30
Purchase #3	$66.72	9.338%	$72.9503	$72.95	$72.95	$73.00
Purchase #4	$178.76	9.317%	$195.4151	$195.42	$195.40	$195.40
Purchase #5	$140.70	11.219%	$156.4851	$156.49	$156.50	$156.50
Purchase #6	$193.59	12.178%	$217.1654	$217.17	$217.15	$217.20
Purchase #7	$86.65	3.557%	$89.7321	$89.73	$89.75	$89.70
7 purchase totals =	$971.24		$1,051.5425	$1,051.56	$1,051.55	$1,051.60