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	$129.27	10.140%	$142.378	$142.38	$142.40	$142.40
Purchase #2	$165.31	10.307%	$182.3485	$182.35	$182.35	$182.30
Purchase #3	$32.49	4.344%	$33.9014	$33.90	$33.90	$33.90
Purchase #4	$141.88	7.329%	$152.2784	$152.28	$152.30	$152.30
Purchase #5	$38.43	9.625%	$42.1289	$42.13	$42.15	$42.10
Purchase #6	$223.32	10.814%	$247.4698	$247.47	$247.45	$247.50
Purchase #7	$219.83	9.618%	$240.9732	$240.97	$240.95	$241.00
7 purchase totals =	$950.53		$1,041.4782	$1,041.48	$1,041.50	$1,041.50