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	$215.53	6.127%	$228.7355	$228.74	$228.75	$228.70
Purchase #2	$137.34	7.861%	$148.1363	$148.14	$148.15	$148.10
Purchase #3	$139.74	13.566%	$158.6971	$158.70	$158.70	$158.70
Purchase #4	$104.91	4.682%	$109.8219	$109.82	$109.80	$109.80
Purchase #5	$60.34	7.404%	$64.8076	$64.81	$64.80	$64.80
Purchase #6	$192.33	3.395%	$198.8596	$198.86	$198.85	$198.90
Purchase #7	$158.74	5.739%	$167.8501	$167.85	$167.85	$167.90
7 purchase totals =	$1,008.93		$1,076.9081	$1,076.92	$1,076.90	$1,076.90