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	$30.55	8.454%	$33.1327	$33.13	$33.15	$33.10
Purchase #2	$134.79	5.646%	$142.4002	$142.40	$142.40	$142.40
Purchase #3	$16.64	6.372%	$17.7003	$17.70	$17.70	$17.70
Purchase #4	$53.78	3.828%	$55.8387	$55.84	$55.85	$55.80
Purchase #5	$90.38	10.461%	$99.8347	$99.83	$99.85	$99.80
Purchase #6	$153.27	6.280%	$162.8954	$162.90	$162.90	$162.90
Purchase #7	$196.69	10.740%	$217.8145	$217.81	$217.80	$217.80
7 purchase totals =	$676.10		$729.6165	$729.61	$729.65	$729.50