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	$193.44	11.831%	$216.3259	$216.33	$216.35	$216.30
Purchase #2	$202.29	6.693%	$215.8293	$215.83	$215.85	$215.80
Purchase #3	$72.42	11.789%	$80.9576	$80.96	$80.95	$81.00
Purchase #4	$55.87	6.182%	$59.3239	$59.32	$59.30	$59.30
Purchase #5	$55.84	4.686%	$58.4567	$58.46	$58.45	$58.50
Purchase #6	$117.38	9.363%	$128.3703	$128.37	$128.35	$128.40
Purchase #7	$128.86	9.437%	$141.0205	$141.02	$141.00	$141.00
7 purchase totals =	$826.10		$900.2842	$900.29	$900.25	$900.30