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	$53.90	13.864%	$61.3727	$61.37	$61.35	$61.40
Purchase #2	$68.41	6.573%	$72.9066	$72.91	$72.90	$72.90
Purchase #3	$165.53	12.588%	$186.3669	$186.37	$186.35	$186.40
Purchase #4	$154.55	9.199%	$168.7671	$168.77	$168.75	$168.80
Purchase #5	$73.60	10.390%	$81.247	$81.25	$81.25	$81.20
Purchase #6	$49.56	6.260%	$52.6625	$52.66	$52.65	$52.70
Purchase #7	$149.29	10.106%	$164.3772	$164.38	$164.40	$164.40
7 purchase totals =	$714.84		$787.7000	$787.71	$787.65	$787.80