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	$221.93	10.192%	$244.5491	$244.55	$244.55	$244.50
Purchase #2	$79.79	8.259%	$86.3799	$86.38	$86.40	$86.40
Purchase #3	$244.88	9.669%	$268.5574	$268.56	$268.55	$268.60
Purchase #4	$126.92	11.284%	$141.2417	$141.24	$141.25	$141.20
Purchase #5	$13.59	7.665%	$14.6317	$14.63	$14.65	$14.60
Purchase #6	$238.45	12.213%	$267.5719	$267.57	$267.55	$267.60
Purchase #7	$120.81	5.729%	$127.7312	$127.73	$127.75	$127.70
7 purchase totals =	$1,046.37		$1,150.6629	$1,150.66	$1,150.70	$1,150.60