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	$110.57	4.538%	$115.5877	$115.59	$115.60	$115.60
Purchase #2	$169.44	9.621%	$185.7418	$185.74	$185.75	$185.70
Purchase #3	$222.91	6.797%	$238.0612	$238.06	$238.05	$238.10
Purchase #4	$30.94	3.741%	$32.0975	$32.10	$32.10	$32.10
Purchase #5	$117.47	5.798%	$124.2809	$124.28	$124.30	$124.30
Purchase #6	$208.90	11.470%	$232.8608	$232.86	$232.85	$232.90
Purchase #7	$112.60	3.480%	$116.5185	$116.52	$116.50	$116.50
7 purchase totals =	$972.83		$1,045.1484	$1,045.15	$1,045.15	$1,045.20