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	$215.73	11.728%	$241.0308	$241.03	$241.05	$241.00
Purchase #2	$113.41	13.491%	$128.7101	$128.71	$128.70	$128.70
Purchase #3	$106.69	11.480%	$118.938	$118.94	$118.95	$118.90
Purchase #4	$157.82	4.642%	$165.146	$165.15	$165.15	$165.10
Purchase #5	$77.56	4.802%	$81.2844	$81.28	$81.30	$81.30
Purchase #6	$128.74	9.187%	$140.5673	$140.57	$140.55	$140.60
Purchase #7	$73.69	5.857%	$78.006	$78.01	$78.00	$78.00
7 purchase totals =	$873.64		$953.6826	$953.69	$953.70	$953.60