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	$67.41	10.488%	$74.48	$74.48	$74.50	$74.50
Purchase #2	$112.27	12.771%	$126.608	$126.61	$126.60	$126.60
Purchase #3	$247.50	6.105%	$262.6099	$262.61	$262.60	$262.60
Purchase #4	$229.58	4.299%	$239.4496	$239.45	$239.45	$239.40
Purchase #5	$82.63	9.606%	$90.5674	$90.57	$90.55	$90.60
Purchase #6	$85.96	6.428%	$91.4855	$91.49	$91.50	$91.50
Purchase #7	$185.98	3.842%	$193.1254	$193.13	$193.15	$193.10
7 purchase totals =	$1,011.33		$1,078.3258	$1,078.34	$1,078.35	$1,078.30