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	$158.34	8.159%	$171.259	$171.26	$171.25	$171.30
Purchase #2	$245.48	5.635%	$259.3128	$259.31	$259.30	$259.30
Purchase #3	$125.38	13.411%	$142.1947	$142.19	$142.20	$142.20
Purchase #4	$61.76	11.154%	$68.6487	$68.65	$68.65	$68.60
Purchase #5	$59.73	12.215%	$67.026	$67.03	$67.05	$67.00
Purchase #6	$143.73	10.457%	$158.7598	$158.76	$158.75	$158.80
Purchase #7	$171.72	5.154%	$180.5704	$180.57	$180.55	$180.60
7 purchase totals =	$966.14		$1,047.7714	$1,047.77	$1,047.75	$1,047.80