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	$198.41	8.832%	$215.9336	$215.93	$215.95	$215.90
Purchase #2	$21.34	3.631%	$22.1149	$22.11	$22.10	$22.10
Purchase #3	$87.37	9.216%	$95.422	$95.42	$95.40	$95.40
Purchase #4	$90.78	10.593%	$100.3963	$100.40	$100.40	$100.40
Purchase #5	$100.48	8.740%	$109.262	$109.26	$109.25	$109.30
Purchase #6	$171.98	5.304%	$181.1018	$181.10	$181.10	$181.10
Purchase #7	$147.56	10.389%	$162.89	$162.89	$162.90	$162.90
7 purchase totals =	$817.92		$887.1206	$887.11	$887.10	$887.10