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	$81.65	7.312%	$87.6202	$87.62	$87.60	$87.60
Purchase #2	$205.63	6.685%	$219.3764	$219.38	$219.40	$219.40
Purchase #3	$19.31	11.830%	$21.5944	$21.59	$21.60	$21.60
Purchase #4	$91.46	12.501%	$102.8934	$102.89	$102.90	$102.90
Purchase #5	$156.43	5.188%	$164.5456	$164.55	$164.55	$164.50
Purchase #6	$212.41	11.376%	$236.5738	$236.57	$236.55	$236.60
Purchase #7	$95.31	10.443%	$105.2632	$105.26	$105.25	$105.30
7 purchase totals =	$862.20		$937.8670	$937.86	$937.85	$937.90