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	$62.91	10.661%	$69.6168	$69.62	$69.60	$69.60
Purchase #2	$160.94	4.254%	$167.7864	$167.79	$167.80	$167.80
Purchase #3	$93.90	6.765%	$100.2523	$100.25	$100.25	$100.30
Purchase #4	$165.85	3.265%	$171.265	$171.27	$171.25	$171.30
Purchase #5	$177.34	8.722%	$192.8076	$192.81	$192.80	$192.80
Purchase #6	$134.74	4.742%	$141.1294	$141.13	$141.15	$141.10
Purchase #7	$176.89	10.792%	$195.98	$195.98	$196.00	$196.00
7 purchase totals =	$972.57		$1,038.8375	$1,038.85	$1,038.85	$1,038.90