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	$187.41	4.599%	$196.029	$196.03	$196.05	$196.00
Purchase #2	$132.53	7.436%	$142.3849	$142.38	$142.40	$142.40
Purchase #3	$161.83	8.187%	$175.079	$175.08	$175.10	$175.10
Purchase #4	$18.51	9.494%	$20.2673	$20.27	$20.25	$20.30
Purchase #5	$124.34	4.464%	$129.8905	$129.89	$129.90	$129.90
Purchase #6	$36.31	13.803%	$41.3219	$41.32	$41.30	$41.30
Purchase #7	$115.70	10.668%	$128.0429	$128.04	$128.05	$128.00
7 purchase totals =	$776.63		$833.0155	$833.01	$833.05	$833.00