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	$50.69	12.333%	$56.9416	$56.94	$56.95	$56.90
Purchase #2	$219.83	6.243%	$233.554	$233.55	$233.55	$233.60
Purchase #3	$163.87	10.655%	$181.3303	$181.33	$181.35	$181.30
Purchase #4	$31.78	3.547%	$32.9072	$32.91	$32.90	$32.90
Purchase #5	$227.95	5.443%	$240.3573	$240.36	$240.35	$240.40
Purchase #6	$236.88	3.453%	$245.0595	$245.06	$245.05	$245.10
Purchase #7	$75.33	5.244%	$79.2803	$79.28	$79.30	$79.30
7 purchase totals =	$1,006.33		$1,069.4302	$1,069.43	$1,069.45	$1,069.50