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	$105.55	3.453%	$109.1946	$109.19	$109.20	$109.20
Purchase #2	$204.72	5.697%	$216.3829	$216.38	$216.40	$216.40
Purchase #3	$196.76	7.150%	$210.8283	$210.83	$210.85	$210.80
Purchase #4	$184.38	12.834%	$208.0433	$208.04	$208.05	$208.00
Purchase #5	$37.82	6.777%	$40.3831	$40.38	$40.40	$40.40
Purchase #6	$169.30	6.775%	$180.7701	$180.77	$180.75	$180.80
Purchase #7	$198.63	10.839%	$220.1595	$220.16	$220.15	$220.20
7 purchase totals =	$1,097.16		$1,185.7618	$1,185.75	$1,185.80	$1,185.80