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	$164.92	4.558%	$172.4371	$172.44	$172.45	$172.40
Purchase #2	$104.41	5.793%	$110.4585	$110.46	$110.45	$110.50
Purchase #3	$208.43	13.530%	$236.6306	$236.63	$236.65	$236.60
Purchase #4	$213.90	10.829%	$237.0632	$237.06	$237.05	$237.10
Purchase #5	$188.34	13.535%	$213.8318	$213.83	$213.85	$213.80
Purchase #6	$214.51	3.874%	$222.8201	$222.82	$222.80	$222.80
Purchase #7	$54.76	12.123%	$61.3986	$61.40	$61.40	$61.40
7 purchase totals =	$1,149.27		$1,254.6399	$1,254.64	$1,254.65	$1,254.60