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	$40.74	13.704%	$46.323	$46.32	$46.30	$46.30
Purchase #2	$183.35	5.782%	$193.9513	$193.95	$193.95	$194.00
Purchase #3	$58.71	7.112%	$62.8855	$62.89	$62.90	$62.90
Purchase #4	$241.63	3.469%	$250.0121	$250.01	$250.00	$250.00
Purchase #5	$93.82	4.415%	$97.9622	$97.96	$97.95	$98.00
Purchase #6	$238.56	7.112%	$255.5264	$255.53	$255.55	$255.50
Purchase #7	$121.35	9.522%	$132.9049	$132.90	$132.90	$132.90
7 purchase totals =	$978.16		$1,039.5654	$1,039.56	$1,039.55	$1,039.60