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	$30.53	4.317%	$31.848	$31.85	$31.85	$31.80
Purchase #2	$110.37	3.649%	$114.3974	$114.40	$114.40	$114.40
Purchase #3	$193.80	7.540%	$208.4125	$208.41	$208.40	$208.40
Purchase #4	$104.57	6.871%	$111.755	$111.76	$111.75	$111.80
Purchase #5	$109.30	6.129%	$115.999	$116.00	$116.00	$116.00
Purchase #6	$142.70	9.117%	$155.71	$155.71	$155.70	$155.70
Purchase #7	$245.56	9.751%	$269.5046	$269.50	$269.50	$269.50
7 purchase totals =	$936.83		$1,007.6265	$1,007.63	$1,007.60	$1,007.60