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	$64.84	8.830%	$70.5654	$70.57	$70.55	$70.60
Purchase #2	$197.80	4.678%	$207.0531	$207.05	$207.05	$207.10
Purchase #3	$54.70	12.383%	$61.4735	$61.47	$61.45	$61.50
Purchase #4	$85.68	5.458%	$90.3564	$90.36	$90.35	$90.40
Purchase #5	$234.48	6.526%	$249.7822	$249.78	$249.80	$249.80
Purchase #6	$175.89	11.787%	$196.6222	$196.62	$196.60	$196.60
Purchase #7	$187.52	4.656%	$196.2509	$196.25	$196.25	$196.30
7 purchase totals =	$1,000.91		$1,072.1037	$1,072.10	$1,072.05	$1,072.30