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	$241.76	8.840%	$263.1316	$263.13	$263.15	$263.10
Purchase #2	$56.32	5.460%	$59.3951	$59.40	$59.40	$59.40
Purchase #3	$210.67	9.853%	$231.4273	$231.43	$231.45	$231.40
Purchase #4	$211.68	3.611%	$219.3238	$219.32	$219.30	$219.30
Purchase #5	$79.51	12.726%	$89.6284	$89.63	$89.65	$89.60
Purchase #6	$6.33	9.628%	$6.9395	$6.94	$6.95	$6.90
Purchase #7	$98.30	6.653%	$104.8399	$104.84	$104.85	$104.80
7 purchase totals =	$904.57		$974.6856	$974.69	$974.75	$974.50