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	$114.77	7.299%	$123.1471	$123.15	$123.15	$123.10
Purchase #2	$108.37	7.835%	$116.8608	$116.86	$116.85	$116.90
Purchase #3	$186.33	6.163%	$197.8135	$197.81	$197.80	$197.80
Purchase #4	$175.47	7.646%	$188.8864	$188.89	$188.90	$188.90
Purchase #5	$174.78	6.853%	$186.7577	$186.76	$186.75	$186.80
Purchase #6	$90.32	11.131%	$100.3735	$100.37	$100.35	$100.40
Purchase #7	$186.31	10.514%	$205.8986	$205.90	$205.90	$205.90
7 purchase totals =	$1,036.35		$1,119.7376	$1,119.74	$1,119.70	$1,119.80