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	$67.87	11.786%	$75.8692	$75.87	$75.85	$75.90
Purchase #2	$37.55	7.725%	$40.4507	$40.45	$40.45	$40.50
Purchase #3	$238.28	11.207%	$264.984	$264.98	$265.00	$265.00
Purchase #4	$250.54	3.396%	$259.0483	$259.05	$259.05	$259.00
Purchase #5	$65.76	13.744%	$74.7981	$74.80	$74.80	$74.80
Purchase #6	$76.29	3.358%	$78.8518	$78.85	$78.85	$78.90
Purchase #7	$242.39	5.633%	$256.0438	$256.04	$256.05	$256.00
7 purchase totals =	$978.68		$1,050.0459	$1,050.04	$1,050.05	$1,050.10