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	$227.70	6.425%	$242.3297	$242.33	$242.35	$242.30
Purchase #2	$115.49	13.732%	$131.3491	$131.35	$131.35	$131.30
Purchase #3	$103.87	5.466%	$109.5475	$109.55	$109.55	$109.50
Purchase #4	$232.68	4.657%	$243.5159	$243.52	$243.50	$243.50
Purchase #5	$167.52	9.140%	$182.8313	$182.83	$182.85	$182.80
Purchase #6	$40.31	3.302%	$41.641	$41.64	$41.65	$41.60
Purchase #7	$89.43	9.786%	$98.1816	$98.18	$98.20	$98.20
7 purchase totals =	$977.00		$1,049.3961	$1,049.40	$1,049.45	$1,049.20