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	$127.47	5.797%	$134.8594	$134.86	$134.85	$134.90
Purchase #2	$161.63	7.607%	$173.9252	$173.93	$173.95	$173.90
Purchase #3	$78.48	9.661%	$86.062	$86.06	$86.05	$86.10
Purchase #4	$67.86	8.142%	$73.3852	$73.39	$73.40	$73.40
Purchase #5	$237.64	11.753%	$265.5698	$265.57	$265.55	$265.60
Purchase #6	$210.48	13.143%	$238.1434	$238.14	$238.15	$238.10
Purchase #7	$93.26	11.652%	$104.1267	$104.13	$104.15	$104.10
7 purchase totals =	$976.82		$1,076.0717	$1,076.08	$1,076.10	$1,076.10