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	$42.97	12.661%	$48.4104	$48.41	$48.40	$48.40
Purchase #2	$89.85	7.130%	$96.2563	$96.26	$96.25	$96.30
Purchase #3	$115.95	3.106%	$119.5514	$119.55	$119.55	$119.60
Purchase #4	$119.48	13.600%	$135.7293	$135.73	$135.75	$135.70
Purchase #5	$28.67	3.105%	$29.5602	$29.56	$29.55	$29.60
Purchase #6	$78.96	13.272%	$89.4396	$89.44	$89.45	$89.40
Purchase #7	$177.95	7.666%	$191.5916	$191.59	$191.60	$191.60
7 purchase totals =	$653.83		$710.5388	$710.54	$710.55	$710.60