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	$235.30	13.793%	$267.7549	$267.75	$267.75	$267.80
Purchase #2	$76.53	6.739%	$81.6874	$81.69	$81.70	$81.70
Purchase #3	$121.43	8.816%	$132.1353	$132.14	$132.15	$132.10
Purchase #4	$94.83	9.231%	$103.5838	$103.58	$103.60	$103.60
Purchase #5	$166.55	11.595%	$185.8615	$185.86	$185.85	$185.90
Purchase #6	$200.95	4.127%	$209.2432	$209.24	$209.25	$209.20
Purchase #7	$132.25	11.349%	$147.2591	$147.26	$147.25	$147.30
7 purchase totals =	$1,027.84		$1,127.5252	$1,127.52	$1,127.55	$1,127.60