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	$52.90	9.568%	$57.9615	$57.96	$57.95	$58.00
Purchase #2	$64.71	13.148%	$73.2181	$73.22	$73.20	$73.20
Purchase #3	$90.96	11.460%	$101.384	$101.38	$101.40	$101.40
Purchase #4	$65.44	11.734%	$73.1187	$73.12	$73.10	$73.10
Purchase #5	$101.86	9.361%	$111.3951	$111.40	$111.40	$111.40
Purchase #6	$133.26	6.605%	$142.0618	$142.06	$142.05	$142.10
Purchase #7	$249.28	5.663%	$263.3967	$263.40	$263.40	$263.40
7 purchase totals =	$758.41		$822.5359	$822.54	$822.50	$822.60