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	$113.71	8.450%	$123.3185	$123.32	$123.30	$123.30
Purchase #2	$24.65	12.117%	$27.6368	$27.64	$27.65	$27.60
Purchase #3	$160.64	10.856%	$178.0791	$178.08	$178.10	$178.10
Purchase #4	$176.90	4.760%	$185.3204	$185.32	$185.30	$185.30
Purchase #5	$137.27	3.523%	$142.106	$142.11	$142.10	$142.10
Purchase #6	$65.62	13.577%	$74.5292	$74.53	$74.55	$74.50
Purchase #7	$243.62	11.364%	$271.305	$271.31	$271.30	$271.30
7 purchase totals =	$922.41		$1,002.2950	$1,002.31	$1,002.30	$1,002.20