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	$152.74	13.614%	$173.534	$173.53	$173.55	$173.50
Purchase #2	$99.79	9.413%	$109.1832	$109.18	$109.20	$109.20
Purchase #3	$74.61	4.650%	$78.0794	$78.08	$78.10	$78.10
Purchase #4	$248.99	11.835%	$278.458	$278.46	$278.45	$278.50
Purchase #5	$241.65	6.507%	$257.3742	$257.37	$257.35	$257.40
Purchase #6	$51.89	5.126%	$54.5499	$54.55	$54.55	$54.50
Purchase #7	$175.28	11.398%	$195.2584	$195.26	$195.25	$195.30
7 purchase totals =	$1,044.95		$1,146.4371	$1,146.43	$1,146.45	$1,146.50