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	$238.49	10.725%	$264.0681	$264.07	$264.05	$264.10
Purchase #2	$73.81	12.719%	$83.1979	$83.20	$83.20	$83.20
Purchase #3	$89.78	7.440%	$96.4596	$96.46	$96.45	$96.50
Purchase #4	$148.55	3.253%	$153.3823	$153.38	$153.40	$153.40
Purchase #5	$81.47	6.713%	$86.9391	$86.94	$86.95	$86.90
Purchase #6	$98.39	7.600%	$105.8676	$105.87	$105.85	$105.90
Purchase #7	$105.85	3.234%	$109.2732	$109.27	$109.25	$109.30
7 purchase totals =	$836.34		$899.1878	$899.19	$899.15	$899.30