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	$39.78	8.253%	$43.063	$43.06	$43.05	$43.10
Purchase #2	$238.51	13.372%	$270.4036	$270.40	$270.40	$270.40
Purchase #3	$155.63	7.653%	$167.5404	$167.54	$167.55	$167.50
Purchase #4	$58.71	4.796%	$61.5257	$61.53	$61.55	$61.50
Purchase #5	$147.82	9.744%	$162.2236	$162.22	$162.20	$162.20
Purchase #6	$177.54	9.742%	$194.8359	$194.84	$194.85	$194.80
Purchase #7	$113.86	4.346%	$118.8084	$118.81	$118.80	$118.80
7 purchase totals =	$931.85		$1,018.4006	$1,018.40	$1,018.40	$1,018.30