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	$185.81	12.846%	$209.6792	$209.68	$209.70	$209.70
Purchase #2	$17.97	6.539%	$19.1451	$19.15	$19.15	$19.10
Purchase #3	$212.89	9.574%	$233.2721	$233.27	$233.25	$233.30
Purchase #4	$168.82	12.483%	$189.8938	$189.89	$189.90	$189.90
Purchase #5	$171.64	11.493%	$191.3666	$191.37	$191.35	$191.40
Purchase #6	$37.92	9.183%	$41.4022	$41.40	$41.40	$41.40
Purchase #7	$161.56	10.864%	$179.1119	$179.11	$179.10	$179.10
7 purchase totals =	$956.61		$1,063.8709	$1,063.87	$1,063.85	$1,063.90