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	$111.86	5.835%	$118.387	$118.39	$118.40	$118.40
Purchase #2	$69.51	11.447%	$77.4668	$77.47	$77.45	$77.50
Purchase #3	$62.80	10.525%	$69.4097	$69.41	$69.40	$69.40
Purchase #4	$73.91	11.431%	$82.3587	$82.36	$82.35	$82.40
Purchase #5	$215.56	12.426%	$242.3455	$242.35	$242.35	$242.30
Purchase #6	$191.71	9.292%	$209.5237	$209.52	$209.50	$209.50
Purchase #7	$89.75	7.850%	$96.7954	$96.80	$96.80	$96.80
7 purchase totals =	$815.10		$896.2868	$896.30	$896.25	$896.30