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	$179.27	4.465%	$187.2744	$187.27	$187.25	$187.30
Purchase #2	$112.62	10.233%	$124.1444	$124.14	$124.15	$124.10
Purchase #3	$226.25	7.516%	$243.255	$243.26	$243.25	$243.30
Purchase #4	$57.98	6.684%	$61.8554	$61.86	$61.85	$61.90
Purchase #5	$77.49	9.247%	$84.6555	$84.66	$84.65	$84.70
Purchase #6	$83.39	10.788%	$92.3861	$92.39	$92.40	$92.40
Purchase #7	$202.79	9.874%	$222.8135	$222.81	$222.80	$222.80
7 purchase totals =	$939.79		$1,016.3843	$1,016.39	$1,016.35	$1,016.50