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	$235.52	4.442%	$245.9818	$245.98	$246.00	$246.00
Purchase #2	$160.97	8.653%	$174.8987	$174.90	$174.90	$174.90
Purchase #3	$119.76	9.621%	$131.2821	$131.28	$131.30	$131.30
Purchase #4	$82.98	8.417%	$89.9644	$89.96	$89.95	$90.00
Purchase #5	$156.85	5.683%	$165.7638	$165.76	$165.75	$165.80
Purchase #6	$158.92	8.550%	$172.5077	$172.51	$172.50	$172.50
Purchase #7	$41.27	12.423%	$46.397	$46.40	$46.40	$46.40
7 purchase totals =	$956.27		$1,026.7955	$1,026.79	$1,026.80	$1,026.90