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	$115.27	10.405%	$127.2638	$127.26	$127.25	$127.30
Purchase #2	$131.66	9.685%	$144.4113	$144.41	$144.40	$144.40
Purchase #3	$222.96	5.453%	$235.118	$235.12	$235.10	$235.10
Purchase #4	$121.80	13.630%	$138.4013	$138.40	$138.40	$138.40
Purchase #5	$82.86	9.585%	$90.8021	$90.80	$90.80	$90.80
Purchase #6	$207.41	12.864%	$234.0912	$234.09	$234.10	$234.10
Purchase #7	$134.63	6.459%	$143.3258	$143.33	$143.35	$143.30
7 purchase totals =	$1,016.59		$1,113.4135	$1,113.41	$1,113.40	$1,113.40